Instruments and methods for inserting artificial intervertebral implants

ABSTRACT

Apparatus and methods for preparing a disc space and inserting an intervertebral disc implant therein are disclosed. Among the various instruments disclosed are a midline marker, a reference pin drill and insertion guide, a fin drill guide, a chisel guide, a sizer, a serrated broach, an implant dispenser, and an implant insertion tool. Methods of utilizing these tools are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Patent Application No. 61/011,554 filed Jan. 18, 2008, thedisclosure of which is hereby incorporated herein by reference.

The present application is related to U.S. patent application Ser. No.11/439,808, entitled “Intervertebral Disc and Insertion MethodsTherefor,” filed May 24, 2006, which claims the benefit of the filingdates of U.S. Provisional Patent Application Nos. 60/790,415, filed Apr.7, 2006, 60/721,053, filed Sep. 27, 2005, 60/701,306, filed Jul. 21,2005 and 60/685,295, filed May 27, 2005, the disclosures of which arehereby incorporated by reference herein.

The present application also relates to U.S. Pat. No. 6,908,484,entitled “Cervical Disc Replacement” and filed on Mar. 6, 2003; U.S.Pat. No. 6,994,728, entitled “Cervical Disc Replacement Method” andfiled on Feb. 11, 2004; United States Patent Application Publication No.2004/0176851, entitled “Cervical Disc Replacement” and filed on Feb. 11,2004; U.S. Pat. No. 6,994,729, entitled “Cervical Disc Replacement” andfiled on Feb. 11, 2004; U.S. Pat. No. 6,997,955, entitled “Cervical DiscReplacement” and filed on Feb. 11, 2004; U.S. Pat. No. 6,972,037,entitled “Cervical Disc Replacement” and filed on Feb. 11, 2004; U.S.Pat. No. 6,972,038, entitled “Cervical Disc Replacement” and filed onFeb. 11, 2004; U.S. Pat. No. 6,997,954, entitled “Cervical DiscReplacement Method” and filed on Feb. 11, 2004; United States PatentApplication Publication No. 2005/0240272, entitled “Cervical DiscReplacement” and filed on May 9, 2005; United States Patent ApplicationPublication No. 2005/0240271, entitled “Cervical Disc Replacement” andfiled on May 9, 2005; United States Patent Application Publication No.2005/0240270, entitled “Cervical Disc Replacement” and filed on May 9,2005; U.S. Pat. No. 6,896,676, entitled “Instrumentation And Methods ForUse In Implanting A Cervical Disc Replacement Device” and filed on Oct.17, 2003; United States Patent Application Publication No. 2004/0176773,entitled “Instrumentation And Methods For Use In Implanting A CervicalDisc Replacement Device” and filed on Feb. 18, 2004; United StatesPatent Application Publication No. 2004/0176843, entitled“Instrumentation And Methods For Use In Implanting A Cervical DiscReplacement Device” and filed on Feb. 18, 2004; United States PatentApplication Publication No. 2004/0176778, entitled “Instrumentation AndMethods For Use In Implanting A Cervical Disc Replacement Device” andfiled on Feb. 18, 2004; United States Patent Application Publication No.2004/0176777, entitled “Instrumentation And Methods For Use InImplanting A Cervical Disc Replacement Device” and filed on Feb. 18,2004; United States Patent Application Publication No. 2004/0176852,entitled “Instrumentation And Methods For Use In Implanting A CervicalDisc Replacement Device” and filed on Feb. 18, 2004; United StatesPatent Application Publication No. 2004/0176774, entitled“Instrumentation And Methods For Use In Implanting A Cervical DiscReplacement Device” and filed on Feb. 18, 2004; United States PatentApplication Publication No. 2004/0176772, entitled “Instrumentation AndMethods For Use In Implanting A Cervical Disc Replacement Device” andfiled on Feb. 18, 2004; United States Patent Application Publication No.2004/0220590, entitled “Instrumentation And Methods For Use InImplanting A Cervical Disc Replacement Device” and filed on Feb. 18,2004; United States Patent Application Publication No. 2005/0071013,entitled “Instrumentation And Methods For Use In Implanting A CervicalDisc Replacement Device” and filed on Nov. 19, 2004; and United StatesPatent Application Publication No. 2004/0193272, entitled“Instrumentation And Methods For Use In Implanting A Cervical DiscReplacement Device” and filed on Feb. 19, 2004, the disclosures of whichare hereby incorporated by reference herein.

The present application also relates to U.S. Pat. No. 6,607,559,entitled “Trial Intervertebral Distraction Spacers” and filed on Jul.16, 2001; U.S. patent application Ser. No. 10/436,039, entitled “TrialIntervertebral Spacers” and filed May 12, 2003; U.S. patent Ser. No.10/128,619, entitled “Intervertebral Spacer Having A Flexible Wire MeshVertebral Body Contact Element” and filed Apr. 23, 2002; U.S. patentapplication Ser. No. 11/073,987, entitled Intervertebral Spacer Having AFlexible Wire Mesh Vertebral Body Contact Element; U.S. patentapplication Ser. No. 10/140,153, entitled “Artificial IntervertebralDisc Having A Flexible Wire Mesh Vertebral Body Contact Element” andfiled May 7, 2002; U.S. patent application Ser. No. 10/151,280, entitled“Tension Bearing Artificial Disc Providing A Centroid Of MotionCentrally Located Within An Intervertebral Space” and filed May 20,2002; U.S. patent application Ser. No. 10/175,417, entitled “ArtificialIntervertebral Disc Utilizing A Ball Joint Coupling” and filed Jun. 19,2002; U.S. patent application Ser. No. 10/256,160, entitled “ArtificialIntervertebral Disc” and filed Sep. 26, 2002; U.S. patent applicationSer. No. 10/294,983, entitled “Artificial Intervertebral Disc Having ACaptured Ball And Socket Joint With A Solid Ball And Retaining Cap” andfiled Nov. 14, 2002; U.S. patent application Ser. No. 10/294,982,entitled “Artificial Intervertebral Disc” and filed Nov. 14, 2002; U.S.patent application Ser. No. 10/294,981, entitled “ArtificialIntervertebral Disc Having A Captured Ball And Socket Joint With A SolidBall And Compression Locking Post” and filed Nov. 14, 2002; U.S. patentapplication Ser. No. 10/642,523, entitled “Axially CompressibleArtificial Intervertebral Disc Having Limited Rotation Using A CapturedBall and Socket” and filed Aug. 15, 2003; U.S. patent application Ser.No. 10/642,522, entitled Artificial Intervertebral Disc Having ACircumferentially Buried Wire Mesh Endplate Attachment Device and filedAug. 15, 2003; U.S. patent application Ser. No. 11/073,987, entitled“Intervertebral Spacer Device Having A Circumferentially Buried WireMesh Endplate Attachment Device” and filed Aug. 15, 2003; U.S. patentapplication Ser. No. 10/642,526, entitled “Circumferentially BuriedWired Mesh Endplate Attachment Device For Use With An Orthopedic Device”and filed Aug. 15, 2003; U.S. patent application Ser. No. 10/294,984,entitled “Artificial Intervertebral Disc Having Limited Rotation Using ACaptured Ball And Socket Joint With A Retaining Cap And A Solid BallHaving A Protrusion” and filed Nov. 14, 2002; U.S. patent applicationSer. No. 10/294,985, entitled “Artificial Intervertebral Disc HavingLimited Rotation Using A Captured Ball and Socket Joint With ACompression” and filed Ser. No. 10/294,985; U.S. patent application Ser.No. 10/294,980, entitled “Artificial Intervertebral Disc Having LimitedRotation Using A Captured Ball And Socket Joint With A Solid Ball, ARetaining Cap, And An Interference Pin” and filed Nov. 14, 2002; U.S.patent application Ser. No. 10/294,986, entitled “ArtificialIntervertebral Disc Having Limited Rotation Using A Captured Ball andSocket Joint With A Solid Ball, A Compression Locking Post, And AnInterference Pin” and filed Nov. 14, 2002; U.S. patent application Ser.No. 10/282,356, entitled “Artificial Intervertebral Disc” and filed Sep.26, 2002; U.S. patent application Ser. No. 10/784,646, entitledArtificial Intervertebral Disc Trial Having A Controllably SeparableDistal End” and filed Feb. 23, 2004; U.S. patent application Ser. No.10/309,585, entitled “Static Trials And Related Instruments and MethodsFor Use In Implanting An Artificial Intervertebral Disc” and filed Dec.4, 2002; U.S. patent application Ser. No. 10/784,637, entitled“Instrumentation For Properly Seating An Artificial Disc In AnIntervertebral Space” and filed Feb. 23, 2004; U.S. patent applicationSer. No. 10/783,153, entitled “Parallel Distractor And Related MethodsFor Use In Implanting An Artificial Intervertebral Disc” and filed Feb.20, 2004, the disclosures of which are hereby incorporated by referenceherein.

BACKGROUND OF THE INVENTION

The present invention is directed to a spinal joint replacement implantand more particularly to a cervical intervertebral disc implant havingsaddle shaped articulating surfaces and to methods of inserting thecervical intervertebral disc implant.

As is well known to those skilled in the art, the structure of theintervertebral disc disposed between the cervical bones in the humanspine comprises a peripheral fibrous shroud (the annulus) whichcircumscribes a spheroid of flexibly deformable material (the nucleus).The nucleus comprises a hydrophilic, elastomeric cartilaginous substancethat cushions and supports the separation between the bones while alsopermitting articulation of the two vertebral bones relative to oneanother to the extent such articulation is allowed by the other softtissue and bony structures surrounding the disc. The additional bonystructures that define pathways of motion in various modes include theposterior joints (the facets) and the lateral intervertebral joints (theunco-vertebral joints). Soft tissue components, such as ligaments andtendons, constrain the overall segmental motion as well.

Traumatic, genetic, and long term wearing phenomena contribute to thedegeneration of the nucleus in the human spine. This degeneration ofthis critical disc material, from the hydrated, elastomeric materialthat supports the separation and flexibility of the vertebral bones, toa flattened and inflexible state, has profound effects on the mobility(instability and limited ranges of appropriate motion) of the segment,and can cause significant pain to the individual suffering from thecondition. Although the specific causes of pain in patients sufferingfrom degenerative disc disease of the cervical spine have not beendefinitively established, it has been recognized that pain may be theresult of neurological implications (nerve fibers being compressed)and/or the subsequent degeneration of the surrounding tissues (thearthritic degeneration of the facet joints) as a result of their beingoverloaded.

Traditionally, the treatment of choice for physicians caring forpatients who suffer from significant degeneration of the cervicalintervertebral disc is to remove some, or all, of the damaged disc. Ininstances in which a sufficient portion of the intervertebral discmaterial is removed, or in which much of the necessary spacing betweenthe vertebrae has been lost (significant subsidence), restoration of theintervertebral separation is required.

Unfortunately, until the advent of spine arthroplasty devices, the onlymethods known to surgeons to maintain the necessary disc heightnecessitated the immobilization of the segment. Immobilization isgenerally achieved by attaching metal plates to the anterior orposterior elements of the cervical spine, and the insertion of someosteoconductive material (autograft, allograft, or other porousmaterial) between the adjacent vertebrae of the segment. Thisimmobilization and insertion of osteoconductive material has beenutilized in pursuit of a fusion of the bones, which is a procedurecarried out on tens of thousands of pain suffering patients per year.

This sacrifice of mobility at the immobilized, or fused, segment,however, is not without consequences. It was traditionally held that thepatient's surrounding joint segments would accommodate any additionalarticulation demanded of them during normal motion by virtue of thefused segment's immobility. While this is true over the short-term(provided only one, or at most two, segments have been fused), theeffects of this increased range of articulation demanded of theseadjacent segments has recently become a concern. Specifically, anincrease in the frequency of returning patients who suffer fromdegeneration at adjacent levels has been reported.

Whether this increase in adjacent level deterioration is trulyassociated with rigid fusion, or if it is simply a matter of theindividual patient's predisposition to degeneration is unknown. Eitherway, however, it is clear that a progressive fusion of a long sequenceof vertebrae is undesirable from the perspective of the patient'squality of life as well as from the perspective of pushing a patient toundergo multiple operative procedures.

While spine arthroplasty has been developing in theory over the pastseveral decades, and has even seen a number of early attempts in thelumbar spine show promising results, it is only recently thatarthroplasty of the spine has become a truly realizable promise. Thefield of spine arthroplasty has several classes of devices. The mostpopular among these are: (a) the nucleus replacements, which arecharacterized by a flexible container filled with an elastomericmaterial that can mimic the healthy nucleus; and (b) the total discreplacements, which are designed with rigid baseplates that house amechanical articulating structure that attempts to mimic and promote thehealthy segmental motion.

Among these solutions, the total disc replacements have begun to beregarded as the most probable long-term treatments for patients havingmoderate to severe lumbar disc degeneration. In the cervical spine, itis likely that these mechanical solutions will also become the treatmentof choice. At present, there are two devices being tested clinically inhumans for the indication of cervical disc degeneration. The first ofthese is the Bryan disc, disclosed in part in U.S. Pat. No. 6,001,130.The Bryan disc is comprised of a resilient nucleus body disposed inbetween concaval-covex upper and lower elements that retain the nucleusbetween adjacent vertebral bodies in the spine. The concaval-convexelements are L-shaped supports that have anterior wings that acceptbones screws for securing to the adjacent vertebral bodies.

The second of these devices being clinically tested is the Bristol disc,disclosed substantially in U.S. Pat. No. 6,113,637. The Bristol disc iscomprised of two L-shaped elements, with corresponding ones of the legsof each element being interposed between the vertebrae and in oppositionto one another. The other of the two legs are disposed outside of theintervertebral space and include screw holes through which the elementsmay be secured to the corresponding vertebra; the superior element beingsecured to the upper vertebral body and the inferior element beingattached to the lower vertebral body. The opposing portions of each ofthe elements comprise the articulating surfaces that include anelliptical channel formed in the lower element and a convexhemispherical structure disposed in the channel.

As is evident from the above descriptions, the centers of rotation forboth of these devices, which are being clinically tested in humansubjects, is disposed at some point in the disc space. More particularlywith respect to the Bryan disc, the center of rotation is maintained ata central portion of the nucleus, and hence in the center of the discspace. The Bristol disc, as a function of its elongated channel (itselongated axis being oriented along the anterior to posteriordirection), has a moving center of rotation which is at all timesmaintained within the disc space at the rotational center of thehemispherical ball (near the top of the upper element).

Thus, there remains a need for improved intervertebral discs, as well asnew and improved methods for safely and efficiently implantingintervertebral discs.

BRIEF SUMMARY OF THE INVENTION

Disclosed herein are intervertebral discs or implants, surgicalinstruments and procedures in accordance with certain preferredembodiments of the present invention. It is contemplated, however, thatthe implants, instruments and procedures may be slightly modified,and/or used in whole or in part and with or without other instruments orprocedures, and still fall within the scope of the present invention.Although the present invention may discuss a series of steps in aprocedure, the steps can be accomplished in a different order, or beused individually, or in subgroupings of any order, or in conjunctionwith other methods, without deviating from the scope of the invention.

In certain preferred embodiments of the present invention, a method ofinserting an intervertebral disc into a disc space includes accessing aspinal segment having a first vertebral body, a second vertebral bodyand a disc space between the first and second vertebral bodies, securinga first pin to the first vertebral body and a second pin to the secondvertebral body, and using the first and second pins for distracting thedisc space. The method preferably includes providing an inserter holdingthe intervertebral disc, engaging the inserter with the first and secondpins, and advancing at least a portion of the inserter toward the discspace for inserting the intervertebral disc into the disc space, whereinthe first and second pins align and guide the inserter toward the discspace.

In certain preferred embodiments, the inserter desirably includes aninserter head having an upper channel and a lower channel. During theadvancing step, the first pin is preferably in contact with the upperchannel and the second pin is preferably in contact with the lowerchannel. The channels may taper inwardly toward one another for urgingthe first and second pins away from one another as the inserter advancestoward the disc space (preferably to more fully open the disc space asthe inserter advances toward the disc space). In certain preferredembodiments, the inserter head has a distal end adapted to contactvertebral bone and a proximal end, and the upper and lower channelstaper inwardly toward one another between the proximal and distal endsof the inserter head. As a result, the channels are closer together nearthe distal end of the inserter than near the proximal end of theinserter. In preferred embodiments, the inserter head includes distallyextending arms for securing an intervertebral disc implant. Each of thedistally extending arms may include an inwardly extending projectionengageable with the intervertebral disc implant.

In other preferred embodiments of the present invention, a method ofinserting an intervertebral disc implant into a disc space includesaccessing a spinal segment having a first vertebral body, a secondvertebral body and a disc space between the first and second vertebralbodies, securing a first pin to the first vertebral body and a secondpin to the second vertebral body, and using the first and second pinsfor distracting the disc space. The method may include engaging a chiselguide having a distal head with the first and second pins, and advancingthe chisel guide toward the disc space for inserting the distal head ofthe chisel guide into the disc space, whereby the first and second pinsalign and guide the chisel guide as the chisel guide advances toward thedisc space. The method may also include coupling a chisel having one ormore cutting blades with the chisel guide and advancing the one or morecutting blades toward the first and second vertebral bodies for formingchannels in one or more endplates of the first and second vertebralbodies. The distal head of the chisel guide preferably has a top surfacewith at least one groove formed therein for guiding the one or morechisel blades toward the disc space. The bottom surface of the head mayalso have at least one groove for guiding the chisel.

The method may also include providing an inserter holding anintervertebral disc implant, and after forming channels in the one ormore endplates of the first and second vertebral bodies, disengaging thechisel guide from the first and second pins and engaging the inserterwith the first and second pins. The inserter is preferably advancedtoward the disc space for inserting the intervertebral disc implant intothe disc space, whereby the first and second pins align and guide theinserter as the inserter advances toward the disc space.

In other preferred embodiments of the present invention, a kit includesa plurality of two-part intervertebral disc implants having differentsizes, and a plurality of implant dispensers, each implant dispenserholding together the two parts of one of the two-part intervertebraldisc implants so that it can be manipulated as a single implantableunit. Each implant dispenser preferably has indicia corresponding to thesize of the intervertebral disc implant held by the implant dispenser.The indicia on the implant dispenser may include a color code or textindicating the size of the intervertebral disc implant held by theimplant dispenser.

In particular preferred embodiments, each intervertebral disc implanthas a top element including a bone engaging surface and an articulatingsurface and a bottom element including a bone engaging surface and anarticulating surface. The implant dispenser desirably holds thearticulating surfaces of the top and bottom elements in contact with oneanother.

The implant dispensers may be flexible. In preferred embodiments, animplant dispenser includes a first arm engaging a top element of theintervertebral disc implant, a second arm engaging a bottom element ofthe intervertebral disc implant, and a connecting element forinterconnecting the first and second arms. The connecting element ispreferably flexible for enabling the first and second arms to move awayfrom one another for releasing the intervertebral disc.

The kit may also include a plurality of inserters, the inserters beingadapted to couple with the intervertebral disc implants while theintervertebral disc implants are held in the implant dispensers, so thatthe intervertebral disc implants can be transferred from the implantdispensers to the inserters. Each inserter preferably has indiciacorresponding to the size of a corresponding one of the intervertebraldisc implants. The indicia on the inserter may include a color code ortext. The intervertebral disc implants are preferably transferable fromthe implant dispensers to the inserters while being maintained as asingle implantable unit. In certain preferred embodiments, an implantinserter will couple directly to the intervertebral disc implant whilethe disc implant is held by an implant dispenser.

In other preferred embodiments of the present invention, a template formarking score lines on a spinal segment includes a shaft having aproximal end and a distal end, and a template marker provided at thedistal end of the shaft. The template marker preferably includes acruciform-shaped structure having a first vertical arm and a secondvertical arm that extends away from the first arm, the first and secondvertical arms being aligned with one another along a first axis. Thecruciform-shaped structure also preferably includes a first lateral armand a second lateral arm extending away from the first lateral arm, thefirst and second lateral arms being aligned with one another along asecond axis, whereby distal surfaces of the first and second lateralarms form a concave curved surface that conforms to an anterior surfaceof a disc between superior and inferior vertebral bodies.

The template may include a central pin or a plurality of pins providedat the distal ends of the lateral arms for being inserted into thenatural disc for stabilizing the template adjacent the disc space, andthe vertical arms and the lateral arms spread outwardly from the distalend of the shaft. The first vertical arm desirably includes a firstdistally extending tack for engaging an anterior surface of the firstvertebral body and the second vertical arm desirably includes a seconddistally extending tack for engaging an anterior surface of the secondvertebral body.

In an alternative embodiment, instead of or in addition to a template,the present invention may include a midline marker. The midline markeris preferably used for determining a midline of a disc space between twovertebrae. The midline marker preferably has a cruciform shape with afirst vertical extension, a second vertical extension, a first lateralextension, and a second lateral extension. The midline marker alsopreferably has a leading face and a trailing face. The leading face mayhave a concave curved surface that extends between the first and secondlateral arms. The first lateral arm preferably has a first barbed spikeprojecting therefrom, and the second lateral arm preferably has a secondbarbed spike projecting therefrom. The midline marker also may include abutton projecting from the rear surface thereof, which is connected tothe midline marker via connector segment. This button may facilitateconnection of the midline marker to a handle.

In certain preferred embodiments of the present invention, each of thetop and bottom elements of the implant has an anterior wall thatpreferably connects the anterior ends of the protrusions on the element.The anterior wall preferably serves as a vertebral body stop to preventover-insertion of the implant and/or posterior migration of the implant.The anterior wall preferably serves as an engageable feature forengagement with instruments, including but not limited to tamps,extraction or repositioning instruments. The anterior wall in someembodiments may have a curved posterior face to sit flush against acurved anterior endplate face. At least the posterior surface of thewall may be coated with an osteoconductive material to facilitatelong-term fixation to the endplate surface.

In certain preferred embodiments of the present invention, theintervertebral disc implants includes a top element and a bottomelement. Each implant part may have protrusions with outwardly laterallyfacing surfaces. One or more of the outwardly laterally facing surfacesmay have a vertically extending channel, or groove, or depression, orlike feature for engagement with instruments, including but not limitedto insertion, extraction or repositioning instruments. Preferably, thesurface of this feature can be coated with an osteoconductive materialto facilitate long-term fixation to the endplate bone.

In certain preferred embodiments, the intervertebral disc implant, orthe instruments, may alternatively or additionally incorporate any orall of the features discussed previously, disclosed herein, or discussedin U.S. patents and/or patent applications incorporated by referenceherein. Preferably, the configuration of the bearing surfaces of theintervertebral disc implant in this preferred embodiment may besubstantially similar to those of the other bearing surfaceconfigurations discussed previously, disclosed herein, or incorporatedby reference herein.

Prior to insertion of the intervertebral disc implant disclosed herein,a surgeon preferably performs a cervical anterior exposure and initialnatural disc removal (e.g., discectomy). After simple exposure andinitial natural disc removal, the surgeon may introduce a guide, such asa reference pin drill guide that enables the surgeon to anchor a pair ofalignment or reference pins (e.g., Caspar pins) into the adjacentvertebral bones, preferably along the midline of the bones, and atpredetermined vertical distances from the endplate edges.

The present application discloses the use of reference or alignment pinsfor properly aligning tooling and/or implants with bone. The referenceor alignment pins shown herein are merely representative examples ofcertain preferred embodiments of the present invention. It iscontemplated that other reference or alignment tools and techniques maybe used for properly aligning tools and/or implants with bone, and thatthese other reference or alignment tools and techniques are within thescope of the present invention.

With the reference pins in place, the surgeon may apply distraction tothe disc space by using a distraction tool, such as a standard Caspardistractor, and then complete the discectomy and distraction. Once thedisc space is cleared and restored to a desired height, the surgeon maychoose to remove the distraction tools and advance a guide, such as aburr or drill guide along the reference pins and into the disc space.The burr or drill guide preferably engages the reference pins as theburr/drill guide is advanced toward the disc space. Thus, the referencepins serve to provide proper alignment of the burr/drill guide relativeto the disc space. In certain preferred embodiments, the burr/drillguide includes a distal head that fits within the disc space. Theburr/drill guide preferably permits the surgeon to introduce a burr ordrill bit through each of four holes in the guide and burr or drillpilot grooves or holes at predetermined locations in the endplates. Aswill be described in more detail below, the pilot grooves are used toform protrusion channels for the protrusions of the intervertebral disc.

In certain preferred embodiments of the present invention, in order tocut protrusion channels in the endplates, a chisel guide may beutilized. The chisel guide preferably includes a distal head that isinsertable into the disc space. The distal head preferably has groovesformed in top and bottom surfaces of the distal head for guiding achisel for cutting protrusion channels. The chisel guide preferably hasalignment openings for sliding over the reference pins. The referencepins preferably align and direct the chisel guide into the disc space.Chisels may then be advanced along the sides of the chisel guide forcutting the protrusion channels. In certain preferred embodiments of thepresent invention, a first pair of chisels (e.g., roughening chisels) isadvanced along the sides of chisel guide to cut channels. Preferably,the first pair of chisels cuts channels that are approximately 1 mmwide. A second pair of larger chisels (e.g., finishing chisels) can beused to widen the protrusion channels, preferably to about 2 mm. Inother preferred embodiments of the present invention, a first pair ofchisels is approximately 1 mm wide and 1.5 mm high, and a second pair ofchisels (e.g., the finishing chisels) are 1.5 mm wide and 2.5 mm high.

Once the protrusion channels have been cut, the implant may be mountedto an insertion tool (e.g., to the distal tip of an insertion tool) andinserted into the disc space. The insertion tool preferably includesupper and lower guide slots or openings that permit the insertion toolto slide along the reference pins. The guide slots are preferably rampedso that the disc space is distracted (to preferably approximately 2 mmwider than the height of the implant) to ensure easy insertion of theimplant. In other preferred embodiments, the reference pins may also beengaged by a distraction tool to distract the disc space duringinsertion, e.g., if such distraction is necessary. This additionaldistraction may ensure that the device is implanted easily withoutrequiring excessive impacting.

Once the intervertebral disc implant has been inserted into the discspace, a tamping instrument may be used to adjust the final position ofthe disc components relative to one another and/or relative to thevertebral bones. Should the surgeon want to remove the deviceintra-operatively, or in the case of a revision, a proximal feature ofthe device (e.g., an anterior wall) may be engaged by an instrument(e.g., an extraction instrument) to pull the device free from the discspace.

In other preferred procedures, after simple exposure and initial discremoval, the surgeon may introduce a guide, such as a reference pingrill guide, that permits the surgeon to drill guide holes in superiorand inferior vertebral bodies (preferably parallel to one another) forthe placement of the pair of reference pins. A second guide, such as asleeve or reference pin driver guide may be used to ensure that thereference pins are placed in the pre-drilled holes so that the pins areparallel, and are driven into the adjacent vertebral bones preferablyalong the midline of the bones, and at predetermined distances from theendplates.

With the reference pins in place, the surgeon may apply distraction tothe disc space, e.g., by means of a distraction tool, and then completethe discectomy and distraction. The surgeon should preferably remove anyanterior or posterior osteophytes that may interfere with the ultimateplacement of the implant.

It should be noted that features and methods and functionalities of thepresent invention, including but not limited to features and methods andfunctionalities for engaging one tool (or parts thereof) with one ormore other tools (or parts thereof) or with the implants (or partsthereof), and vice-versa; for addressing, avoiding, manipulating, orengaging the patient's anatomy; for aligning one or more tools withanatomic or non-anatomic reference points; and for aligning the toolsand implants with one another and/or a treatment space; are not andshould not be limited to those embodied in and achieved by thestructures and methods of the specific embodiments described and shown,but rather the structures and methods of the specific embodimentsdescribed and shown are merely examples of structures and methods thatcan achieve certain features and methods and functionalities of thepresent invention.

One aspect of the present invention includes an assembly for determiningthe midline of a disc space between two vertebrae. In accordance withone embodiment of this aspect, the assembly includes a handle having anouter shaft and a plunger disposed within the outer shaft, the plungerincluding an opening formed in one end. The assembly also preferablyincludes a midline marker having a cruciform-shaped structure andincluding a first lateral extension having a first barbed spikeextending in a first direction, a second lateral extension that extendsaway from said first lateral extension so that the first and secondlateral extension being aligned with one another along a first axis, thesecond lateral extension including a second barbed spike extending inthe first direction, a first vertical extension, a second verticalextension extending away from said first vertical extension, the firstand second vertical extensions being aligned with one another along asecond axis, and a button extending in second direction opposite thefirst direction, the button disposed within the opening formed in theplunger.

In accordance with other embodiments of this aspect, the first andsecond lateral extensions may form a concave curved surface thatconforms to an anterior surface of the disc between the superior andinferior vertebral bodies. The first vertical extension may include afirst concave recess and the second vertical extension includes a secondconcave recess, the first and second concave recesses providing analignment feature for marking the two vertebrae. The plunger may bemoveable with respect to the outer shaft. The plunger may be moveablebetween a first position in which the midline marker is capable of beingremoved from the handle and a second position in which the midlinemarker is fixed to the handle. The plunger may be biased to the secondposition, including, but not limited to, by the inclusion of a spring.The midline marker may be axially fixed with respect to the handle. Theouter shaft may include at least one slot and the plunger includes atleast one pin disposed within the at least one slot. The outer shaft mayinclude an alignment feature. The first vertical extension may include afirst concave recess and the second vertical extension may include asecond concave recess, the first and second concave recesses beingaligned with the alignment feature and providing an alignment featurefor marking the two vertebrae.

Another aspect of the present invention includes a method of markingfirst and second adjacent vertebral bodies separated by anintervertebral disc. In accordance with one embodiment of this aspect,the method includes the steps of providing a midline marker including afirst lateral extension having a first barbed spike direction, a secondlateral extension having a second barbed spike, a first verticalextension including a first recess, and a second vertical extensionincluding a second recess, inserting the first and second barbed spikesin the intervertebral disc so that the first recess is aligned with thefirst vertebral body and the second recess is aligned with the secondvertebral body, using the first recess to mark the first vertebral bodyand the second recess to mark the second vertebral body.

In accordance with other embodiments of this aspect, the first andsecond lateral extensions may be aligned with one another along a firstaxis and the first and second vertical extensions may be aligned withone another along a second axis. The inserting step may include placinga concave curved surface formed by the first and second lateralextensions adjacent the intervertebral disc. The method may furtherinclude the step of attaching the midline marker to a handle having anouter shaft and plunger disposed within the outer shaft. The step ofattaching may include placing a button formed on the midline marker inan opening formed in the plunger. The step of attaching may includemoving the plunger to a first position with respect to the outer shaft,the first position allowing for the button to be placed in the opening.The step of attaching may include moving the plunger to a secondposition with respect to the outer shaft, the second position allowingfor the midline marker to be fixed with respect to the handle. The stepof attaching may include aligning the first and second recesses with analignment feature of the handle. The step of inserting may includealigning the alignment feature with respect to the first and secondvertebral bodies.

Another aspect of the present invention includes a reference pin drilland insertion guide for use in preparing adjacent first and secondvertebral bodies separated by a disc space. In one embodiment of thisaspect, the reference pin drill and insertion guide includes a handle, ashaft connected to the handle, and a head connected to the shaft. Thehead may include a tapered nose capable of being inserted into the discspace, the tapered nose including a top surface and a bottom surface, afirst vertebral body stop disposed to a first side of the tapered noseand extending above the top surface and below the bottom surface, asecond vertebral body stop disposed to a second side of the tapered noseand extending above the top surface and below the bottom surface, afirst protective sheath including a first opening, and a secondprotective sheath including a second opening. When the tapered nose isinserted into the disc space, the first and second protective sheathspreferably enable reference pin holes to be formed in the first andsecond vertebral bodies and reference pins to be place in the first andsecond vertebral bodies.

In other embodiments of this aspect, the shaft may include an elbow sothat the handle is located out of alignment with the head, where theelbow may form an angle of one hundred fifty degrees. The first andsecond vertebral body stops may extend at least two millimeters abovethe top surface and at least two millimeters below the bottom surface.The first and second vertebral body stops may form at least one concavesurface that conforms with the first and second vertebral bodies. Thetapered nose may include first and second surfaces formed parallel toeach other and third and fourth surfaces formed non-parallel to eachother. A stepped drill may be inserted into the first or secondprotective sheath. The first protective sheath may include a first slotand the second protective sheath may include a second slot.

Yet another aspect of the present invention is an implant dispenser forholding the top and bottom elements of an intervertebral disc implant.In accordance with one embodiment of this aspect, the dispenser includesa superior arm for engaging the top element of the intervertebral discimplant, an inferior arm for engaging the bottom element of theintervertebral disc implant, a central support connecting the superiorand inferior arms, the central support allowing for the superior andinferior arms to flex relative to one another, and a clip insertedbetween the superior and inferior arms to prevent the superior andinferior arms from moving towards one another.

In other embodiments of this aspect, the superior and inferior arms mayinclude lateral notches for receiving teeth of the top and bottomelement of the intervertebral disc implant. The superior arm may includea slot and a first notch and the inferior arm may include a secondnotch. The clip may include a main body having an upper end and a lowerend, the upper end disposed within the first notch and the lower enddisposed within the second notch. The clip may include a projectionextending from the main body, the projection disposed within the slot ofthe superior arm.

Yet another aspect of the present invention is an insertion tool forinserting an intervertebral disc implant. In one embodiment of thisaspect the insertion tool an inserter body having a first slot and aninserter head integrally connected with the inserter body. The inserterhead includes a second slot, a first arm including a first inwardlyfacing surface having a first projection extending therefrom and a firstvertebral body stop, the first projection adapted to engage a firstdepression of the intervertebral disc implant, a second arm including asecond inwardly facing surface having a second projection extendingtherefrom and a second vertebral body stop, the second projectionadapted to engage a second depression of the intervertebral discimplant, an upper alignment groove, and a lower alignment groove. Thefirst and second slots form a first continuous slot.

In other embodiments of this aspect, the insertion tool may furtherinclude a third arm and a fourth arm. The third arm may include a thirdprojection adapted to engage a third depression of the intervertebraldisc implant, and the fourth arm may include a fourth projection adaptedto engage a fourth depression of the intervertebral disc implant. Theinserter body may include a third slot and the inserter head includes afourth slot, the third and fourth slots forming a second continuousslot. The first and second arms may be capable of moving with respect toeach other and the third and fourth arms may be capable of moving withrespect to each other. The first continuous slot may be in communicationwith a first aperture and the second continuous slot may be incommunication with a second aperture. The first and second alignmentgrooves may be tapered with respect to each other. The insertion toolmay further include an insertion tool handle, where the insertion toolhandle includes a plunger rod extending therethrough and a knob having acontact surface for moving the plunger rod within the insertion toolhandle.

These and other preferred embodiments of the present invention will bedescribed in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an intervertebral disc implant, inaccordance with certain preferred embodiments of the present invention.

FIGS. 2A-2H show a top element of the intervertebral disc implant shownin FIG. 1.

FIGS. 3A-3H show a bottom element of the intervertebral disc implantshown in FIG. 1.

FIGS. 4A-4H show other views of the intervertebral disc implant shown inFIG. 1.

FIG. 5 shows a perspective view of the top and bottom elements of theintervertebral disc implant shown in FIG. 1.

FIG. 6A shows an anterior end view of the intervertebral disc implantshown in FIG. 1.

FIG. 6B shows a side elevational view of the intervertebral disc implantshown in FIG. 1.

FIGS. 7A-7D show a template, in accordance with certain preferredembodiments of the present invention.

FIGS. 8A-8D show a template marker, in accordance with other preferredembodiments of the present invention.

FIGS. 9A-9B show the template marker of FIG. 8A being attached to atemplate handle, in accordance with certain preferred embodiments of thepresent invention.

FIGS. 10A-10D show the template marker and the template handle shown inFIGS. 9A-9B.

FIGS. 11A-11D show a reference pin drill guide, in accordance withcertain preferred embodiments of the present invention.

FIG. 12 shows a drill bit used with the reference pin drill guide shownin FIGS. 11A-11D.

FIGS. 13A-13B show the reference pin drill guide of FIGS. 11A-11Dinserted into an intervertebral disc space, in accordance with certainpreferred embodiments of the present invention.

FIGS. 14A-14C show a reference pin insertion guide, in accordance withcertain preferred embodiments of the present invention.

FIGS. 15A-15C show a reference pin, in accordance with certain preferredembodiments of the present invention.

FIG. 16 shows a reference pin, in accordance with another preferredembodiment of the present invention.

FIGS. 17A-17C show a reference pin driver, in accordance with certainpreferred embodiments of the present invention.

FIGS. 18A-18B show a sleeve used with the reference pin insertion guideof FIGS. 14A-14C, in accordance with certain preferred embodiments ofthe present invention.

FIGS. 19A-19C show a distractor, in accordance with certain preferredembodiments of the present invention.

FIGS. 20A-20D show a drill guide, in accordance with certain preferredembodiments of the present invention.

FIGS. 21A-21D show a chisel guide, in accordance with certain preferredembodiments of the present invention.

FIGS. 22A-22D show a chisel used in cooperation with the chisel guide ofFIGS. 21A-21D.

FIG. 23 shows the chisel of FIGS. 22A-22D, coupled with the chisel guideof FIGS. 21A-21D.

FIGS. 24A-24B show a mallet, in accordance with certain preferredembodiments of the present invention.

FIGS. 25A-25D show a sizer, in accordance with certain preferredembodiments of the present invention.

FIGS. 26A-26E show the sizer of FIGS. 25A-25D, coupled with a sizerhandle, in accordance with certain preferred embodiments of the presentinvention.

FIGS. 27A-27D show a trial, in accordance with certain preferredembodiments of the present invention.

FIGS. 28A-28F show an implant dispenser, in accordance with certainpreferred embodiments of the present invention.

FIGS. 29A-29E show the implant dispenser of FIGS. 28A-28F, coupled withthe intervertebral disc implant shown in FIG. 1.

FIGS. 30A-30F-1 show an inserter head for inserting an intervertebraldisc into a disc space, in accordance with certain preferred embodimentsof the present invention.

FIG. 31 shows the inserter head of FIG. 30A and an exploded view of aninserter handle, in accordance with certain preferred embodiments of thepresent invention.

FIGS. 32A-32B show the inserter head and inserter handle of FIG. 31assembled together.

FIGS. 33A-33B show an intervertebral disc implant being transferred froman implant dispenser to an inserter head, in accordance with certainpreferred embodiments of the present invention.

FIGS. 34A-34B show an intervertebral disc implant, coupled with aninserter head, in accordance with certain preferred embodiments of thepresent invention.

FIGS. 35A-35B show an intervertebral disc implant being disengaged froma distal end of an inserter head, in accordance with certain preferredembodiments of the present invention.

FIGS. 36A-36B show a tamp, in accordance with certain preferredembodiments of the present invention.

FIGS. 37A-37D show an extractor, in accordance with certain preferredembodiments of the present invention.

FIGS. 38-74 show a method of inserting an intervertebral disc implant,in accordance with certain preferred embodiments of the presentinvention.

FIG. 75A shows a side view of the intervertebral disc implant shown inFIG. 72.

FIG. 75B shows an anterior end view of the intervertebral disc implantshown in FIG. 73.

FIGS. 76A-76E show a midline marker, in accordance with certainpreferred embodiments of the present invention.

FIGS. 77A-77E show a midline marker handle for the midline marker shownin FIGS. 76A-76E, in accordance with certain preferred embodiments ofthe present invention.

FIG. 78A shows the distal end of the midline marker handle shown in FIG.77E.

FIG. 78B shows an U-shaped capture element extendible from the distalend of the midline marker handle shown in FIG. 78A.

FIG. 79A-79D show a reference pin insertion guide, in accordance withcertain preferred embodiments of the present invention.

FIGS. 80A-80B show a step drill for use with the reference pin insertionguide shown in FIGS. 79A-79D.

FIG. 81 shows the step drill of FIGS. 80A-80B coupled with the referencepin insertion guide of FIGS. 79A-79D.

FIG. 82 shows the reference pin insertion guide of FIGS. 79A-79D coupledwith a reference pin and a driver for advancing the reference pin.

FIG. 83 shows a step drill, in accordance with another preferredembodiment of the present invention.

FIGS. 84A-84B show a reference pin drill guide, in accordance withanother preferred embodiment of the present invention.

FIGS. 85A-85B show the step drill of FIG. 83 coupled with the referencepin drill guide of FIGS. 84A-84B.

FIGS. 86A-86B show a method of forming a reference pin opening in avertebrae using the reference pin drill guide shown in FIGS. 84A-85B.

FIGS. 87A-87D show a fin drill guide, in accordance with certainpreferred embodiments of the present invention.

FIGS. 88A-88D show a chisel guide, in accordance with certain preferredembodiments of the present invention.

FIG. 89 shows two chisels coupled with the chisel guide of FIGS.88A-88D, in accordance with certain preferred embodiments of the presentinvention.

FIGS. 90A-90D show a sizer for preparing a disc space between opposingvertebrae, in accordance with certain preferred embodiments of thepresent invention.

FIGS. 91A-91C show the sizer of FIGS. 90A-90D secured to a distal end ofan insertion handle.

FIGS. 92A-92B show a perspective views of the sizer of FIGS. 90A-90Dsecured to the distal end of the insertion handle shown in FIGS.91A-91C.

FIGS. 93A-93D show a serrated broach used for preparing a disc space, inaccordance with certain preferred embodiments of the present invention.

FIGS. 94A-94F show an implant dispenser, in accordance with otherpreferred embodiments of the present invention.

FIGS. 95A-95C show a clip used with the implant dispenser shown in FIGS.94A-94F.

FIGS. 96A-96E show an intervertebral disc secured by the implantdispenser of FIGS. 94A-94E, whereby the implant dispenser is coupledwith the clip of FIGS. 95A-95C.

FIGS. 97A-97C show an inserter body including an inserter head, inaccordance with certain preferred embodiments of the present invention.

FIG. 97D shows the inserter head shown in FIG. 97A taken along lines97D-97D thereof.

FIG. 97E shows a fragmentary view of the distal end of the inserter headshown in FIG. 97B.

FIG. 97F shows a fragmentary view of the distal end of the inserter headshown in FIG. 97C.

FIGS. 98A-98B show perspective views of the inserter head shown in FIGS.97A-97C.

FIGS. 99A-99B show the implant dispenser and intervertebral disc shownin FIGS. 96A-96E being secured to the inserter head of FIGS. 98A-98B.

FIGS. 100A-100B show the intervertebral disc after it has been securedto the distal end of the inserter head.

FIGS. 101A-101B show the intervertebral disc after being decoupled fromthe distal end of the inserter head by an advancing plunger, inaccordance with certain preferred embodiments of the present invention.

DETAILED DESCRIPTION

Referring to FIG. 1, in certain preferred embodiments of the presentinvention, an intervertebral disc implant 100 includes a top element 102and a bottom element 104. As will be described in more detail below, thetop and bottom elements 102, 104 have opposing articulating surfacesthat engage one another. The intervertebral disc implant is adapted tobe inserted into a disc space between adjacent vertebrae.

Referring to FIGS. 2A-2H, the top element 102 includes a first boneengaging surface 106 having protrusions 108A, 108B and a secondarticulating surface 110. Referring to FIGS. 2C and 2D, the top elementhas a posterior end 112 and an anterior end 114. As shown in FIGS. 2Aand 2C, the two protrusions 108 are interconnected by an anterior wall116 that extends along the anterior end 114 of the top element. Theanterior wall preferably serves as a vertebral body stop to prevent overinsertion of the intervertebral disc implant and/or posterior migrationof the implant. The anterior wall of the top element 102 preferablyprovides an engagement surface to be engaged by instruments, includingbut not limited to tamps and extraction or repositioning instruments. Incertain preferred embodiments, the anterior wall may have a curvedposterior face adapted to sit flush against a curved anterior face of avertebral body. In certain preferred embodiments, one or more surfacesof the anterior wall may be coated with an osteoconductive material tofacilitate long-term fixation to an endplate surface.

Referring to FIGS. 2E and 2H, the articulating surface 110 preferablydefines a convex curve extending between the sides 118, 120 of the topelement 102. Referring to FIGS. 2F and 2G, the articulating surface 110also defines a concave curve or surface extending between the posteriorand anterior ends 112, 114 of the top element 102. In certain preferredembodiments, the articulating surface 110 defines a toroidalsaddle-shaped surface.

Referring to FIG. 2C, each protrusion 108 preferably has an engagementfeature, or depression 121 formed in an outer surface thereof. Incertain preferred embodiments, the depressions 121 are verticallyextending. In other preferred embodiments, the protrusions may have oneor more holes extending at least partially or completely therethrough.The holes may receive or be suitable for receiving a bone-growthinducing material. As will be described in more detail below, thedepressions 121 facilitate engagement of the top element withinstruments, and specifically preferably facilitate securing andhandling of the top element 102 during an intervertebral disc insertionoperation. The depressions 121 on the two protrusions 108 are preferablyin alignment with one another. In other words, the depressions 121 arepreferably at the same distance between the posterior end 112 and theanterior end 114 of the top element 102.

As shown in FIGS. 2A, 2C, and 2F, each protrusion 108 preferablyincludes teeth 122 having sloping surfaces 124 (e.g., having a low pointnearer to the posterior end 112 of the top element 102 and a high pointnearer to the anterior end 114 of the top element 102) that facilitateinsertion of the posterior end 112 of the top element 102. Referring toFIG. 2F, the sloping surfaces 124 of the teeth 122 facilitate insertionof the implant in a direction indicated by arrow D₁. The verticalsurfaces 126 of the teeth 122 hinder or prevent dislodgement of theimplant in the direction indicated by arrow D₂.

Referring to FIG. 2H, the teeth 122 on protrusions 108 preferably alsoinclude laterally sloping surfaces 126 that slope downwardly from apexesclose to axis A₁ to the lateral sides 118, 120 of the top element 102.Thus, the sloping surfaces 126 slope away from axis A₁.

Referring to FIGS. 3A-3H, the intervertebral disc implant preferablyincludes a bottom element 104 having a first bone engaging surface 128and a second articulating surface 130 that engages the articulatingsurface 110 of the top element 102 (FIG. 2A). The bottom element 104includes a posterior end 132, an anterior end 134, and lateral sides136, 138. Referring to FIGS. 3A and 3C, the first bone engaging surface128 includes first and second protrusions 140A, 140B. Each protrusionpreferably has an engagement feature or depression 142 formed in anouter surface thereof. In certain preferred embodiments, the depressions142 are vertically extending. In other preferred embodiments, theprotrusions may have one or more holes extending at least partially orcompletely therethrough. The holes may receive or be suitable forreceiving a bone-growth inducing material. As will be described in moredetail below, the depressions 142 facilitate engagement of the bottomelement with instruments, and specifically preferably facilitatesecuring and handling of the bottom element 104 during an intervertebraldisc insertion operation. The depressions 142 on the two protrusions140A, 140B are preferably in alignment with one another. In other words,the depressions 142 are preferably at the same distance between theposterior end 132 and the anterior end 134 of the bottom element 104.Referring to FIGS. 3F and 3G, each protrusion 140A, 140B preferably alsoincludes teeth 144 having sloping surfaces 146 having a low point nearerto the posterior end 132 of the bottom element 104 and a high pointnearer to the anterior end 134 of the bottom element 104. Similar to thesloping surfaces of the teeth of the top element 102 described above,the sloping surfaces 146 on the teeth 144 facilitate insertion of thebottom element 104 in the direction indicated by arrow D₃. The verticalsurfaces 147 of the teeth 144 hinder or prevent dislodgement of theimplant in the direction indicated by arrow D₄ (FIG. 3).

Referring to FIGS. 3E and 3H, the teeth 144 preferably also includelaterally sloping surfaces 148 that slope downwardly toward axis A₂(FIG. 3H). More specifically, the sloping lateral surfaces have apexesor high points closer to the lateral sides 136, 138 and low points thatare closer to axis A₂.

Referring to FIGS. 3A and 3C, the bottom element 108 also includes ananterior wall 150 that extends between the protrusions 140A, 140B. Theanterior wall preferably serves as a vertebral body stop to prevent overinsertion of the intervertebral disc and/or posterior migration of theimplant. The anterior wall preferably provides an engagement surfacethat can be engaged by instruments, including but not limited to tampsand extraction or repositioning instruments. In certain preferredembodiments, the anterior wall may have a curved posterior face adaptedto sit flush against a curved anterior face of a vertebral body. Incertain preferred embodiments, one or more surfaces of the anterior wallmay be coated with an osteoconductive material to facilitate long-termfixation to an endplate surface.

Referring to FIGS. 3F and 3G, the articulating surface 130 preferablydefines a convex curve or surface extending between the posterior 132and anterior ends 134 of the bottom element 104. Referring to FIGS. 3Eand 3H, the articulating surface 130 preferably defines a concave curveor surface extending between the lateral sides 136, 138 of the bottomelement 104. As will be described in more detail herein, thearticulating surface 130 preferably defines a toroidal saddle-shapedsurface that engages the articulating surface of the top element 102(FIG. 2G).

FIGS. 4A and 4B show the top element 102 of FIG. 2A being coupled withthe bottom element 104 of FIG. 3A. Referring to FIG. 4B, each of the topand bottom elements 102, 104 desirably has a respective anterior wall116, 150 that extends between protrusions. The anterior walls 116, 150preferably extend along the anterior ends 114, 134 of the respective topand bottom elements.

FIG. 4D shows top element 102 including posterior end 112, anterior end114, and lateral sides 118, 120. The top element 102 includes first boneengaging surface 106 and protrusions 108A, 108B having depressions 121formed in outer surfaces thereof. The top element 102 includes anteriorwall 116 extending between protrusions 108A, 108B.

Referring to FIG. 4C, bottom element 104 has a posterior end 132,anterior end 134, and lateral sides 136, 138. The bottom element 104includes bone engaging surface 128 and protrusions 140A, 140B. Theprotrusions include depressions 142 formed in outer surfaces thereof.The bottom element 104 also includes anterior wall 150 extending betweenprotrusions 140A, 140B.

Referring to FIGS. 4E and 4H, the opposing articulating surfaces 110,130 of the top element 102 and the bottom element 104 are adapted toengage one another. The teeth 122 on the top element 102 slopedownwardly toward the posterior end 112 thereof. Similarly, the teeth144 on the bottom element 104 slope downwardly toward the posterior end132 thereof.

Referring to FIGS. 4F and 4G, the teeth 122 on the top element 102 havelateral sloping surfaces 126 that slope downwardly toward the sides 118,120. In contrast, the teeth 144 on the bottom element 104 includelateral sloping surfaces 148 that slope inwardly toward axis A₃ (FIG.4F). As a result, the lateral sloping surfaces 126 of the teeth 122 onthe top element 102 slope in a different direction than the lateralsloping surfaces 148 of the teeth 144 on the bottom element 104. Thus,the apex of the teeth 122 on the top element 102 is closer to axis A₃than the apex of the teeth 144 on the bottom element 104. It has beenobserved that stacking two implants in successive disc spaces may resultin cracking of vertebral bone between the implants because the apexes onthe teeth of the two implants are in alignment. The present inventionseeks to avoid this cracking problem by offsetting the apexes of theteeth on the top element 102 from the apexes of the teeth on the bottomelement 104. Although the present invention is not limited by anyparticular theory of operation, it is believed that providing teethhaving off-set apexes enables two or more intervertebral disc implantsto be inserted into two or more successive disc spaces, while minimizingthe likelihood of cracking the vertebral bodies between the disc spaces.

Referring to FIG. 5, prior to insertion into an intervertebral space,the articulating surface 110 of the top element 102 opposes thearticulating surface 130 of the bottom element 104. In preferredembodiments, the articulating surface 110 of the top element 102 definesa toroidal saddle-shaped surface including a concave surface extendingbetween proximal and anterior ends thereof and a convex surfaceextending between the sides of the top element 102. The articulatingsurface 130 of the bottom element 104 also includes a toroidalsaddle-shaped surface having a convex surface extending between theposterior and anterior ends and a concave surface extending between thesides of the bottom element 104.

The articulating surfaces may be similar to the articulating surfacesdisclosed in commonly assigned U.S. Pat. No. 6,997,955. In certainpreferred embodiments of the present invention, the longitudinallyinwardly directed articulation surface of the top element 102 forms aconstant radii saddle-shaped articulation surface. More particularly,the saddle surface is defined by a concave arc that is sweptperpendicular to and along a convex arc. The articulation surface has across-section in one plane that forms a concave arc, and a cross-sectionin another plane (perpendicular to that plane) that forms a convex arc.The concave arc has a respective constant radius of curvature about anaxis perpendicular to the one plane. The convex arc has a respectiveconstant radius of curvature about an axis perpendicular to the otherplane.

In a preferred embodiment, the concave arc has a constant radius ofcurvature A about an axis perpendicular to the anterior-posterior plane,and the convex arc has a constant radius of curvature B about an axisperpendicular to the lateral plane. Preferably, radius A is less thanradius B.

The longitudinally inwardly directed articulation surface of the bottomelement 104 also preferably forms a constant radii saddle-shapedarticulation surface. More particularly, the saddle surface is definedby a convex arc that is swept perpendicular to and along a concave arc.The articulation surface has a cross-section in one plane that forms aconvex arc, and a cross-section in another plane (perpendicular to thatplane) that forms a concave arc. The convex arc has a respectiveconstant radius of curvature about an axis perpendicular to the oneplane. The concave arc has a respective constant radius of curvatureabout an axis perpendicular to the other plane.

In a preferred embodiment, the convex arc has a constant radius ofcurvature C about an axis perpendicular to the anterior-posterior plane,and the concave arc has a constant radius of curvature D about an axisperpendicular to the lateral plane. Preferably, radius C is less thanradius D.

The constant radii saddle shaped articulation surfaces are configuredand sized to be nestable against one another and articulatable againstone another, to enable adjacent vertebral bones (against which the topand bottom elements are respectively disposed in the intervertebralspace) to articulate in flexion, extension, and lateral bending. Moreparticularly, the intervertebral disc of the present invention isassembled by disposing the top and bottom elements so that the vertebralbody contact surfaces are directed away from one another, and thearticulation surfaces are nested against one another such that theconcave arcs accommodate the convex arcs.

Accordingly, movement of the adjacent vertebral bones relative to oneanother is permitted by the movement of the top and bottom elementsrelative to one another. In flexion and extension, the concave arcs ofthe top element 102 ride on the convex arcs of the bottom element 104about a center of rotation below the articulation surfaces. In lateralbending, the concave arcs of the bottom element 104 ride on the convexarcs of the top element 102 about a center of rotation above thearticulation surfaces. During these articulations, the elements aremaintained at constant relative distraction positions, i.e., theelements do not move in directions that are directed away from oneanother (for example, do not move in opposing axial directions from oneanother (e.g., along a longitudinal axis of the spine)). Accordingly, incertain preferred embodiments, the present invention provides a pair ofarticulation surfaces that have a center of rotation above the surfacesin one mode of motion (e.g., lateral bending), and below the surfaces inanother (e.g., flexion/extension), consistent in these regards with anatural cervical intervertebral joint. Preferably, the articulationsurfaces are sized and configured so that the respective ranges ofangles through which flexion/extension and lateral bending can beexperienced are equal to or greater than the respective normalphysiologic ranges for such movements in the cervical spine.

It is preferable that, in addition to the flexion, extension, andlateral bending motions described above, the adjacent vertebral bones bepermitted by the intervertebral disc implant to axially rotate relativeto one another (e.g., about the longitudinal axis of the spinal column)through a small range of angles without moving in opposite (or otherwisedirected away from one another) directions (e.g., along the longitudinalaxis) within that range, and then to engage in such opposite (orotherwise directed away from one another) movement once that range isexceeded. Preferably, the articulation surfaces are accordinglyconfigured and sized to permit such movements. Because of the differingradii of the opposing articulation surfaces, the top and bottom elementsare able to axially rotate relative to one another about thelongitudinal axis of the spinal column through a range of angles withoutcausing the vertebral body contact surfaces to move away from oneanother along the longitudinal axis. Once the axial rotation exceedsthat range, the articulation surfaces interfere with one another as theconcave arcs move toward positions in which they would be parallel toone another, and the distance between the vertebral body contactsurfaces increases with continued axial rotation as the concave arcsride up against their oppositely directed slopes. Thus, the articulationsurfaces are configurable according to the present invention to permitnormal physiologic axial rotational motion of the adjacent vertebralbones about the longitudinal axis through a range of angles withoutabnormal immediate axially opposite (or otherwise directed away from oneanother) movement, and to permit such axially opposite (or otherwisedirected away from one another) movement when under normal physiologicconditions it should occur, that is, outside that range of angles.

The articulation surfaces preferably maintain contact over a range ofnormal physiologic articulating movement between the adjacent vertebralbones. That is, through flexion, extension, lateral bending, and axialrotation, the articulation surfaces are in contact with one another.Preferably, the surface area dimensions of the articulation surfaces areselected in view of the selected radii of curvature to prevent the edgesof the saddle surfaces (particularly the edges of the concave arcs) fromhitting any surrounding anatomic structures, or other portions of theopposing upper or lower element, before the limit of the normalphysiologic range of an attempted articulation is reached.

FIGS. 6A and 6B show, according to a preferred embodiment of the presentinvention, an intervertebral disc implant 100 including top element 102and bottom element 104. The articulating surface of the top element 102preferably engages the articulating surface of the bottom element 104.The articulating surface of the top element 102 preferably defines aconvex surface extending between lateral sides 118, 120 thereof. Thearticulating surface of the bottom element 104 defines a concave surfaceextending between the lateral sides 136, 138 thereof. Each of the topand bottom elements 102, 104 include respective anterior walls 116, 150that prevent over insertion and/or posterior migration of theintervertebral disc implant 100. The teeth 122 on the protrusions of thetop element 102 include laterally sloping surfaces 124 that slopedownwardly toward the sides 118, 120. In contrast, the teeth 144 on theprotrusions of the bottom element 104 include laterally sloping surfaces148 that preferably slope downwardly toward a central region of thebottom element 104. The opposite sloping configuration of the teeth onthe respective top and bottom elements 102, 104 preferably permitsstacking of two intervertebral disc implants in two successive discspaces, while minimizing the likelihood of cracking the vertebral bonebetween the adjacent disc spaces. In other preferred embodiments, theopposite sloping configuration of the teeth enable three or moreintervertebral discs to be stacked atop one another over three or moresuccessive disc spaces. In still other preferred embodiments, the teethof the top and bottom elements may slope laterally in the samedirection.

Referring to FIG. 6B, the articulating surface of the top element 102defines a concave surface extending between posterior 112 and anterior114 ends thereof. The articulating surface of the bottom element 104defines a convex surface extending between the posterior 132 andanterior 134 ends of the bottom element 104. The teeth 122 on theprotrusions of the top element 102 include sloping surfaces 124 thatslope downwardly toward the posterior end 112 of the top element 102.The teeth 144 on the protrusions of the bottom element 104 have slopingsurfaces 146 that slope downwardly toward the posterior end 132 of thebottom element 104. As a result, the sloping surfaces 124, 146 of therespective teeth 122, 144 slope in the same direction, i.e., toward theposterior ends of the top and bottom elements 102, 104. The respectivesloping surfaces 124, 146 facilitate insertion of the implant 100 into adisc space. The respective vertical surfaces 122, 144 hinder or preventexpulsion or migration of the implant from the disc space after it hasbeen inserted.

Referring to FIGS. 7A-7D in certain preferred embodiments of the presentinvention, a template 154 has a distal end 156 and a proximal end 158.The template 154 includes a shaft 160 extending between the distal andproximal ends and a handle 162 secured to a proximal end of the shaft.The template includes a template marker 164. As shown in FIG. 7D, thetemplate marker 164 has a cruciform-like structure with a firstvertically extending arm 166, a second vertically extending arm 168, afirst lateral arm 170 and a second lateral arm 172. The upper and lowerends of the respective first and second vertically extending arms 166,168 preferably have apexes that may be used for aligning scoring of theanterior faces of the adjacent vertebral bodies. The score marks maylater be used for aligning other tools and/or the intervertebral disc.The template marker 164 includes a central pin 174, a first tack 176 onthe first vertical arm 166 and a second tack 178 on the second verticalarm 168. The central pin 174 is adapted to engage a natural disc and thetacks 176, 178 are adapted to engage bone, such as vertebral bone. Thecentral pin 174 may also be replaced or supplanted by a plurality ofpins positioned on the lateral arms 170, 172. Referring to FIG. 7D, thelateral arms 170, 172 preferably define a distal surface 180 that iscurved for matching the curve of the anterior surface of a naturalintervertebral disc.

FIGS. 8A-8D show a template marker for a template, in accordance withanother preferred embodiment of the present invention. The templatemarker 164′ is substantially similar to the template marker shown inFIG. 7D. However, the template marker 164′ shown in FIGS. 8A-8D includesfirst and second engagement features or projections 182A′ and 182B′projecting from top and bottom surfaces of adapter shaft 184′.

Referring to FIGS. 9A and 9B, the template marker 164′ may be attachedto a distal end 156′ of a template handle 162′. The adapter shaft 184′of the template marker 164′ is inserted into an opening at the distalend 156′ of the template handle 162′. The projections 182A′, 182B′ onthe adapter shaft 184′ are inserted into opposing grooves 186′ formed inthe template handle 162′.

FIGS. 10A-10B show the template marker 164′ secured to the distal end156′ of the template handle 162′. Referring to FIGS. 10A-10 c, after theprojections 182A′ and 182B′ on the template marker 164′ have beenreceived within the grooves at the distal end of the template handle162′, a rotatable handle 188′ is rotated for advancing shaft 190′relative to outer shaft 192′ so as to lock the template marker 164′ tothe distal end 156′ of the template handle 162′. In certain preferredembodiments, the template handle 162′ is rotated to seat the projections182A′, 182B′ in the grooves 186′ and the rotatable handle 188′ isrotated to hold the projections 182A′, 182B′ forward in the grooves186′.

FIGS. 11A-11B show a reference pin drill guide 194 having a distal end196, a proximal end 198, a shaft 200 extending between the distal andproximal ends and a handle 202 at the proximal end of the shaft 200. Thedistal end 196 of the reference pin drill guide includes a main body 204having an upper end 206 and a lower end 208. The main body includes afirst opening 210 extending therethrough adjacent upper end 206 and asecond opening 212 extending therethrough adjacent lower end 208. Themain body includes a head 214 that projects from a distal side thereof.The head includes a tapered nose 216, a top surface 218, and a bottomsurface 220. The head 214 also includes a first vertebral body stop 222projecting upwardly from top surface 218 and a second vertebral bodystop 224 projecting below second surface 220.

Referring to FIGS. 11A and 11C, the shaft 200 of the reference pin drillguide 194 is preferably angled or curved so that the working end of thetool may be observed by a surgeon. As shown in FIGS. 11A-11C, a distalend 226 of a drill bit 228 may be passed through openings 210, 212 forforming holes in the vertebral bone. As will be described in more detailbelow, the threaded ends of reference pins may be inserted into theholes. Referring to FIG. 11A, the main body 204 preferably includes anupper alignment flange 230 projecting from upper end 206 thereof and alower alignment flange 232 projecting from lower end 208 of main body204, for use in aligning the flanges with alignment marks previouslyscored on the vertebral bones.

The drill bit 228 includes a distal end 226 and a proximal end 234adapted to be secured by a drill. The drill bit 228 includes a shoulder236 that limits advancement of the drill bit through the openings 210,212 of the main body 204.

Referring to FIGS. 13A and 13B, in order to make holes in the vertebralbone for alignment or reference pins, the head 214 of the reference pindrill guide 194 is inserted into the disc space between the vertebralbodies. The head is advanced until the vertebral body stops abut theanterior faces of the respective vertebral bodies. The distal end of thedrill bit 228 is then inserted through the openings 210, 212 in the mainbody 204. The distal end of the drill bit 228 is advanced into bone toform the openings for the reference pins.

Referring to FIGS. 14A-14C, in certain preferred embodiments of thepresent invention, a reference pin insertion guide 236 has a distal end238, a proximal end 240, a shaft 242 extending between the distal andproximal ends and a handle 244 secured to the distal end of the shaft242. The reference pin insertion guide 236 includes alignment guide body246 having an upper end including a first opening 248 and a lower endincluding a second opening 250. The distal end also includes a head 252insertable into an intervertebral disc space. The head 252 has a taperednose 254, a top surface 256 terminating at a first vertebral body stop258 and a bottom surface 260 terminating at a second vertebral body stop262. The first and second vertebral body stops 258, 262 preferablyprevent over insertion of the tool into an intervertebral disc space.

FIGS. 15A-15C show an alignment or reference pin 264, in accordance withcertain preferred embodiments of the present invention. Referring toFIGS. 15A and 15B, the reference pin 264 has a distal end 266 and aproximal end 268. Referring to FIG. 15B, the distal end 266 includes athreaded portion 270 that is threadable into vertebral bone. The distalend of reference pin 264 also preferably includes a flange 272 thatlimits insertion of the reference pin. A proximal side of the flange 272includes a feature or hex nut 274 engageable by a driver.

FIG. 16 shows a rescue reference pin 264′, in accordance with anotherpreferred embodiment of the present invention. The rescue pin 264′ issubstantially similar to the reference pin 264 shown in FIG. 15B andincludes a threaded shaft 276′ located on a posterior side of flange272′. The rescue pin 264′ is preferably used if the reference pin 264shown in FIG. 15B does not remain anchored to bone or pulls out of thebone. The rescue pin 264′ preferably has larger diameter threading (thanthe reference pin 264) at the leading end thereof.

Referring to FIGS. 17A-17C, in certain preferred embodiments of thepresent invention, a reference pin driver 280 is utilized for drivingreference pins into bone. The reference pin driver 280 includes a distalend 282 having an opening adapted to receive a reference pin 264 (or arescue pin 264′) and a proximal end 284 including a handle 286. Thereference pin driver 280 also includes a shaft 288 that extends betweenthe distal end 282 and the proximal end 284. The shaft 288 preferablyhas an opening including at least one hexagonal surface that matches thehexagonal nut 274 on the reference pin 264 (FIG. 15A).

FIGS. 18A and 18B show, for use in preferred embodiments of theinvention, a sleeve 290 insertable into the openings in the referencepin drill guide 194. The sleeve 290 includes a distal end 292 having anopening 294 and a proximal end 296 including a stop flange 298.Referring to FIG. 18B, the distal end 292 of sleeve 290 includes opening294 extending therethrough and larger opening 296 at the distal-mostend. The enlarged opening 296 preferably has a circular counterbore thatfreely slides over the hex nut on the reference pin 264 described above.The smaller opening 294 preferably forms a sliding fit with an outersurface of the reference pin 264. The sleeve 290 preferably stabilizesthe reference pin insertion guide 236 after the first reference pin hasbeen inserted into bone and during insertion of the second referencepin.

FIGS. 19A-19C shows a distraction instrument 300 including supportelement 302 and first and second distracting arms 304, 306 that travelover the support element 302. Each distracting arm 304, 306 has a curvedsection 308 and openings 310 at distal ends of the arms 304, 306. Thedistracting element 300 also includes adjustment element 312 thatinteracts with support body 302 and arms 304, 306 for adjusting thedistance between the arms. As will be described in more detail herein,after reference pins 264 are inserted into vertebral bone, thedistractor arms 304, 306 are slid over the reference pins. Once thedistractor element 300 is coupled with the reference pins 264, theadjusting element 312 may be operated for separating the distractor arms304, 305 so as to distract adjacent vertebrae and allow for removal ofdisc material.

Referring to FIGS. 20A-20D, in accordance with certain preferredembodiments of the present invention, a drill guide 314 has a distal end316, a proximal end 318, a shaft 320 extending between the distal andproximal ends and a handle 322 adjacent the distal end 318. The drillguide includes a main body 324 attached to the distal end of the shaft320. Referring to FIG. 20D, the main body 324 includes first and secondopenings 326, 328 for engaging the reference pins. The main body 324also includes four drill guide openings 330A-330D for guiding a distalend 332 of a drill bit 334. The four drill guide openings 330A-330D arepositioned to coincide with the protrusions of an intervertebral discimplant. Referring to FIGS. 20A and 20C, the main body 324 also includesa head 336 insertable into an intervertebral disc space. The head 336includes a tapered nose 338, a top surface 340, a bottom surface 342,and first and second vertebral body stops 344, 346 extending above andbelow the top and bottom surfaces 340, 342. As will be described in moredetail herein, the alignment openings 326, 328 are slid over thereference pins and the tool is advanced until the head 336 is positionedin the intervertebral disc space. The distal end 332 of the drill bit334 is then passed in series through the drill alignment openings330A-330D for at least partially forming protrusion openings for theprotrusions of an intervertebral disc implant.

Referring to FIGS. 21A-21D, in accordance with certain preferredembodiments of the present invention, a chisel guide 350 includes adistal end 352, a proximal end 354 with a handle 356 and a shaft 360extending from the proximal end toward the distal end. The shaft 360includes on one side a left track 362 having an opening 364 at theproximal end 354 and extending toward the distal end 352, and, on anopposite site, a right track 362′ having an opening 364′ at the proximalend 354 and extending toward the distal end 352. The chisel guide 350includes a head 366 at the distal end 352. Referring to FIGS. 21C and21D, the head 366 includes alignment grooves 368 formed in top andbottom surfaces thereof. The alignment grooves are adjacent the left andright tracks of the shaft 360.

Referring to FIGS. 21B and 21D, the chisel guide also includes first andsecond reference pins openings 370, 372. In operation, the reference pinopenings 370, 372 are slid over the reference pins described above, andthe head 366 is inserted into an intervertebral disc space.

Referring to FIGS. 22A-22D, in certain preferred embodiments of thepresent invention, a chisel 374 has a distal end 376 with first andsecond cutting blades 378, 380, and a proximal end 382 having a handle384 and a striking surface 386. The chisel 374 includes a shaft 388extending between the distal and proximal ends of the tool. The shaft388 includes projections extending therefrom for guiding the chisel inthe tracks of the chisel guide shown in FIGS. 21A-21D. Referring toFIGS. 22B and 22D, the projections 390 guide the chisel along the trackwhile maintaining alignment of the chisel. Referring to FIG. 22C, thedistal end of the chisel includes an opening extending between cuttingblades 378, 380. The opening 394 allows the cutting blades 378, 380 toslide over the grooves 368 formed in the top and bottom surfaces of thehead 366 (FIG. 21D).

Referring to FIG. 23, the chisel guide 350 described in FIGS. 21A-21D isslid over the reference pins 264 secured to bone. The chisel 374 ofFIGS. 22A-22D is then slideably advanced along one of the tracks of thechisel guide for forming protrusion openings in the bone. The same or asecond chisel 374 is then slideably advanced along the other of thetracks to form additional protrusion openings in the bone.

FIGS. 24A-24B show a mallet 396 including a handle 398 having a lowerend 400 and an upper end 402 with a striking element 404 secured to theupper end. The striking element 404 includes a U-shaped opening 406formed therein so that the mallet may be used as a slap hammer.

FIGS. 25A-25D show a sizer 408, in accordance with certain preferredembodiments of the present invention. The sizer 408 includes a main body410 having a distal end 412, a top surface 414, and a bottom surface416. The body 410 includes sloping surfaces 418 extending between thedistal end 412 and the top and bottom surfaces 414, 416 to easeinsertion of the sizer between the vertebrae. The sizer 408 alsoincludes an adapter shaft 420 and first and second projections 422A,422B.

The sizer also includes vertebral body stops 424 and 426 for limitinginsertion of the sizer. Referring to FIGS. 25A and 25B, the sizers arepreferably provided in variable heights (e.g., 5-9 mm) and variable baseplate widths (e.g., 14 and 16 mm). Sequentially larger sizers are usedto determine the desired implant height that will best fit into the discspace without over-tensioning the annulus. In their preferred usage, thesizer that fits snugly into the disc space with mild to moderateresistance to pull-out should indicate the proper height of the disc tobe implanted.

Referring to FIGS. 26A-26E, a sizer 408 may be attached to a distal end430 of a handle 432 by sliding the projections 422A, 422B into groovesextending from the distal end 430 of the handle 432. After the sizer 408is coupled with the handle 432, a rotatable element 434 may be rotatedfor locking the sizer 408 to the handle 432. In certain preferredembodiments, the handle 432 is rotated to seat the projections 422A,422B in the grooves extending from the distal end 430 of the handle andthe rotatable element 434 is rotated to hold the projections 422A, 422Bforward in the closed ends of the grooves.

Referring to FIGS. 27A-27D, in certain preferred embodiments of thepresent invention, a trial 436 includes a distal end 438, a proximal end440, a shaft 442 extending between the distal and proximal ends, and astriking surface 444 located at the proximal end 440 of the shaft 442.The trial also includes a trial implant 446 secured at distal end 438.The trial implant 446 includes protrusions 448 having teeth 450 that arepositioned to coincide with the protrusions of a intervertebral implant.The size of the trial implant 446 is selected based upon the largestsizer that safely fit within the intervertebral disc space. The trial436 also includes reference pin alignment openings 452, 454. Thereference pin alignment openings 452, 454 are adapted to slide over thereference pins secured to vertebral bone.

Referring to FIGS. 28A-28F, in accordance with certain preferredembodiments of the present invention, an implant dispenser 456 isadapted to hold the top and bottom elements of an intervertebral discimplant as a single unit with the articulating surfaces held together.Referring to FIGS. 28A-28C, the implant dispenser 456 is preferablyflexible and includes a superior arm 458 for engaging a top element ofan intervertebral disc implant and an inferior arm 460 for engaging abottom element of an intervertebral disc implant. The superior andinferior arms preferably have lateral notches 462 formed therein forreceiving the teeth of the top and bottom elements, as will be describedin more detail herein. The implant dispenser also preferably includes acentral support 464 that enables the superior and inferior arms 458, 460to move away from one another for releasing an intervertebral discimplant.

Referring to FIG. 28E, the superior arm 458 preferably has indicia suchas a text or a symbol 466 indicating that the arm 458 overlies the topelement of the implant. The indicia on the superior arm may alsopreferably include the size 468 of the implant. FIG. 28F shows theinferior arm 460 including indicia such as a text or a symbol 470indicating that the arm 460 overlies the bottom element of the implant.The inferior element indicia may also include size information 472 asshown.

FIGS. 29A-29E show the intervertebral disc implant of FIG. 1 secured inthe implant dispenser 456 of FIGS. 28A-28F. The intervertebral discimplant includes top element 102 engaged by superior arm 458 and centralelement 464. The bottom element 104 is engaged by inferior arm 460 andcentral element 464. The teeth of the implant extend through the notches462 in the superior and inferior arms.

FIGS. 30A to 30F-1 show an inserter head for inserting an intervertebraldisc implant. Referring to FIGS. 30A-30B, the inserter head 474 includesa main body 476 having a distal end 478 and a proximal end 480. Thedistal end 478 of the main body 476 includes four spaced arms 482 havinginwardly facing surfaces with projections 484 that are adapted to fitwithin the depressions formed within the protrusions of the top andbottom elements of the intervertebral disc implant. The main bodyincludes a central opening 486 extending from the proximal end 480 tothe distal end 478 thereof. Referring to FIGS. 30C and 30D, the mainbody 476 also includes an upper alignment groove 488 and a loweralignment groove 490. The alignment grooves 488, 490 are adapted toengage the reference pins for guiding advancement of the inserter head.In certain preferred embodiments, the alignment grooves 488, 490 tapertoward one another so that the grooves are closer to one another atdistal ends thereof and farther away from one another at proximal endsthereof.

FIGS. 30E and 30E-1 show the projection 484 on one of the four arms 482.As noted above, the projections 484 on the arms 482 engage thedepressions in the protrusions of the top and bottom elements of theintervertebral discs.

FIG. 31 shows the inserter head 474 of FIG. 30A prior to assembly withan inserter handle 492. The inserter handle 492 includes a pusher rod494 that may be advanced by a rotatable handle 496 coupled with thepusher rod 494. The handle includes a shaft 496 that is insertable intoopening 486 of the inserter head. Referring to FIGS. 32A and 32B, afterthe inserter head 474 has been coupled with the inserter handle, theelement 496 may be rotated for advancing the pusher rod 494. As will bedescribed in more detail below, advancing the pusher rod 494 willdisengage the top and bottom elements of an intervertebral disc with thearms 482 of the inserter head 474.

FIGS. 33A and 33B show the implant dispenser 456 of FIG. 29A holding anintervertebral disc implant 100. Referring to FIG. 33B, the depressionsin the protrusions are coupled with the projections in the arms 482 ofthe inserter head 474. Referring to FIGS. 34A and 34B, after the implant100 has been secured to the arms 482 of the inserter head 474, theimplant dispenser may be removed. Referring to FIG. 34B, at this point,the implant 100 is held by the arms 482 of the inserter head. Referringto FIGS. 35A-35B, the pusher rod 494 may be advanced toward the distalend of the inserter head 474 for decoupling the implant 100 from theinserter head 474.

Referring to FIGS. 36A and 36B, in accordance with certain preferredembodiments of the present invention, a tamp 500 includes a distal end502, a proximal end 504, a shaft 506 extending between the distal andproximal ends and a handle 508 adjacent the proximal end 504. The distalend 502 includes an abutting surface 510 that is adapted to engage theanterior end of an intervertebral disc implant. The tamp 500 alsoincludes a striking surface 512 at the proximal end. A device such asthe mallet shown and described above may be impacted against thestriking surface 512 for applying force to the striking surface 510 ofthe tamp.

FIGS. 37A-37D show an extractor 514, in accordance with certainpreferred embodiments of the present invention. The extractor 514includes a distal end 516 having a hook 518, a proximal end 520, and ashaft 522 extending between the distal and proximal ends. The extractor514 also preferably includes a handle 524 adjacent the proximal end 520thereof. FIGS. 37C and 37D show shaft 522 with a hook 518 at a distalend of the shaft.

Disclosed herein are implants, surgical instruments and procedures inaccordance with certain preferred embodiments of the present invention.It is contemplated, however, that the implants, instruments andprocedures may be slightly modified, and/or used in whole or in part andwith or without other instruments and procedures, and still fall withinthe scope of the present invention. Although the present invention maydiscuss a series of steps in a procedure, the steps may be accomplishedin a different order, or may be used individually, or in conjunctionwith other methods, without deviating from the scope of the presentinvention.

Prior to implanting the intervertebral disc implant, a review of X-rays,MRI or CT-myelogram is preferably conducted to assess the level to betreated for osteophytes and to compare the intervertebral disc heightwith the adjacent levels. Referring to FIG. 38, the patient ispreferably positioned in the supine position to provide for an anteriorsurgical approach to the cervical spine. Steps should preferably betaken to stabilize the patient's spine in a neutral position and toprevent rotation during the procedure. In certain preferred embodiments,it may be preferable to place a towel or bean bag underneath thepatient's shoulders. Tape, a halter or skeletal traction may be used toprevent rotation. Referring to FIGS. 38 and 39, a transverse skinincision is preferably made at the appropriate level to expose thetargeted spinal segment including the discs above and below the targetspinal segment. Care should be taken to avoid prolonged retractionpressure on vital structures, such as the esophagus.

Another step in the intervertebral disc implantation procedure involvesidentifying and marking a midline on the target segment of the spine. Inpreferred embodiments, a template, such as the template shown anddescribed above in FIGS. 7A-10D, is utilized to mark the midline. Incertain preferred embodiments, the size and dimensions of the templatemay vary. The exact template selected may be based upon initialestimation of the appropriate implant size from pre-operative X-raysand/or MRI/CT. The template is preferably attached to the templatehandle, as described above in reference to FIGS. 9A-9B and 10A-10D. Thetemplate may have different sizes whereby the lateral arms of thetemplate attachments approximate the width options of the implant (i.e.,14 mm and 16 mm). Referring to FIG. 40 and FIG. 9A, the central pin atthe distal end of the template is inserted into the middle of the discso that the upper and lower vertically extending arms are approximatelyaligned with the midline axis of the vertebral column. The tacks on theupper and lower vertical arms engage the vertebral bone to stabilize thetemplate. The handle at the proximal end of the template handle may betapped, such as by using a mallet, to push the tacks into the vertebralbone. The template handle may then be disengaged from the template,which remains attached to the vertebral bone. At this stage, fluoroscopymay be used to verify the midline and lateral margins of the disc space.In addition, the spinous processes are preferably centered.

Referring to FIG. 41, a tool such as a scalpel or an electrocautery toolis preferably utilized to score the midline points on the anteriorsurfaces of the superior and inferior vertebral bodies. Care ispreferably taken to ensure that the midline is well defined for allsubsequent endplate preparation and implant insertion steps. Referringto FIGS. 41 and 42, after the midline points have been scored, thetemplate handle may be reattached to the template for removing thetemplate from engagement with the target area. FIG. 42 shows the targetarea of the spine with an opening formed in the disc space by thecentral pin of the template, and two smaller openings being formed inthe respective superior and inferior vertebral bodies by the tacks ofthe template. In addition, the scoring of the midline points is evidentat the anterior surfaces of the superior and inferior vertebral bodies.

Referring to FIG. 43, a cutting tool such as a scalpel may be used todissect a window in the annulus of the targeted disc. The size of thewindow dissected in the annulus preferably approximates the width of anintervertebral disc implant to be inserted therein. In certain preferredembodiments, radiographic imaging such as fluoroscopy may be used toidentify osteophytes that extend anteriorly. Any osteophytes that extendanteriorly are preferably resected back to the vertebral body so thatthe surfaces of the superior and inferior vertebral bodies areflattened. Moreover, techniques such as radiographic imaging should beused to identify any osteophytes extending downwardly or upwardly intothe anterior region of the disc space. Such osteophytes should beresected to the endplates. FIG. 44 shows the targeted disc space afterthe initial discectomy has been completed including resection of anyanterior osteophytes present in the targeted disc area.

Referring to FIG. 45, after initial preparation of the disc space,reference pins may be attached to the anterior faces of the superior andinferior vertebral bodies. The midline score marks and the tack openingsin the superior and inferior vertebral bodies are preferably used forproper placement of the reference pins. Care is preferably taken toensure proper placement and alignment of the reference pins, which willguide subsequent steps of the procedure. Referring to FIG. 45, thereference pin drill guide described in FIGS. 11A-11D is inserted intothe dissected disc space. Specifically, the head at the distal end ofthe reference pin drill guide is inserted into the disc space betweenthe vertebral bodies. The head at the distal end is inserted until thevertebral body stops abut against the anterior faces of the superior andinferior vertebral bodies. At this stage, one of the openings in themain body of the reference pin drill guide is preferably in alignmentwith the superior vertebral body and another one of the openings is inalignment with the inferior vertebral body. The reference pin drillguide is preferably aligned with the midline of the vertebral bodies asmarked by the score line markings. The alignment of the reference pindrill guide is preferably checked such as by using fluoroscopy.Referring to FIG. 46, with the reference pin drill guide in place, holesare drilled in the superior and inferior vertebral bodies using a drillbit, such as the drill bit shown in FIG. 12 above. FIG. 46 shows a holebeing drilled in the superior vertebral body. FIG. 47 shows a hole beingdrilled in the inferior vertebral body. FIG. 48 shows the target spinalsegment after holes have been drilled in both the superior and inferiorvertebral bodies.

Referring to FIG. 49, after the holes are drilled, the reference pindrill guide is removed from the targeted disc segment. At this stage, afirst hole for a first reference pin has been formed in the superiorvertebral body and a second hole for a second reference pin has beenformed in the inferior vertebral body. The first and second holes in thevertebral bodies are preferably in alignment with the score marks formedpreviously.

Referring to FIG. 50, the reference pins may be inserted using thereference pin insertion guide shown and described above in FIGS.14A-14C. Preferably, the head at the distal end of the reference pininsertion guide is inserted into the disc space until the vertebral bodystops abut against the anterior surfaces of the superior and inferiorvertebral bodies. As shown in FIG. 50, the reference pin insertion guidepreferably has a first opening in alignment with the opening formed inthe superior vertebral body and a second opening aligned with theopening formed in the inferior vertebral body. A reference pin, such asthe reference pin shown and described above in FIGS. 15A-15C is insertedinto the first opening of the reference pin insertion guide. Thethreading at the distal end of the reference pin is threaded into theopening in the superior vertebral body. The reference pin driver shownin FIG. 17A-17C may be utilized for threading the reference pin into thevertebral body. The threads on the reference pins may be self-tappingthreads.

Referring to FIG. 51, after the first reference pin is inserted intobone, the second reference pin is passed through the lower opening inthe reference pin insertion guide and driven into the inferior vertebralbody using the reference pin driver. In other preferred embodiments, afirst reference pin may be attached to the inferior vertebral bodybefore attaching a second reference pin to the superior vertebral body.Thus, the insertion of the reference pins can be accomplished in anyparticular order.

Referring to FIG. 52, in certain preferred embodiments, after a firstreference is inserted into bone, a sleeve such as the sleeve shown anddescribed in FIGS. 18A-18B may be slid over the attached reference pinso as to stabilize the reference pin insertion guide. As shown in FIG.52, the sleeve preferably remains in place to prevent movement of thereference pin insertion guide during insertion of the second referencepin into the other vertebral body.

In particular preferred embodiments, different sized reference pins maybe used. These different sized reference pins may include shafts havingdifferent diameters and/or lengths. In certain preferred embodiments, asmall and a large set of reference pins is provided in an instrumenttray. The smallest of the pair of reference pins should be insertedinitially. If the smaller pair of reference pins proves unsatisfactory,the larger pair of reference pins may be utilized. As shown in FIG. 53,the reference pins are preferably parallel to each other and inalignment with the midline of the superior and inferior vertebralbodies.

Once the reference pins are in place, a surgeon may preferably applydistraction to the disc space by using a distraction tool, such as adistractor as shown and described in FIGS. 19A-19C. Once distraction hasoccurred, the disc space may be cleared of any extraneous matter andrestored to a desired height. Prior to distraction, the facets of thetargeted spinal segment should be reviewed under fluoroscopy in order tomonitor facet orientation during distraction. The distractor shown inFIGS. 19A-19C is preferably placed over the reference pin shown in FIG.53. FIG. 54 shows the distractor after it has been placed over thereference pins. If the reference pins loosen at any time during thedistraction procedure, the reference pins may be removed and replacedwith the larger reference pins provided in the instrument set.

The distractor is then utilized to apply distraction to the targetedspinal segment. During the distraction procedure, the facets and thedisc space are preferably monitored under fluoroscopy to ensure acomplete distraction. The amount of distraction should not exceed theheight of the adjacent disc space. As noted above, fluoroscopy should beused to monitor the distraction height so as to preventover-distraction. As is well known to those skilled in the art,over-distraction may cause nerve and/or facet damage.

After the targeted spinal segment has been distracted, the discectomyprocedure is completed. In preferred embodiments, the posterior andlateral margins of the disc space are cleared of any extraneous matter.The clearing of the posterior and lateral margins preferably extends tothe uncinate processes and all the way back to the nerve root and canal.In certain preferred embodiments, lateral fluoroscopy is utilized tocheck the anterior aspects of the vertebral body for osteophytes. Acutting tool, such as a burr, may be used to further prepare theendplates of the opposing superior and inferior vertebral bodies. Thecutting tool may be utilized to smooth out the curvature of the superiorendplate. After the discectomy has been completed, the endplates of theadjacent vertebral bodies are preferably parallel to one another andrelatively uniform, thereby preventing undersizing of the implant.

In certain preferred embodiments, the decompression of the targeted discspace may be completed by removing any posterior osteophytes or softtissue material that may inhibit the full distraction of the posteriorportion of the targeted disc space. In certain preferred embodiments, itmay be necessary to remove the posterior longitudinal ligament (PLL) toachieve optimal restoration of the disc height, decompression andrelease for post-operative motion. In addition, the posteriolateralcorners of the endplates may be resected as needed to provide neuraldecompression. In certain instances, it may be necessary to remove theposteriolateral uncovertebral joints. The lateral uncovertebral jointsare preferably not removed unless they are causing nerve rootcompression. In addition, in certain preferred embodiments it may benecessary to perform a foraminotomy if there are symptoms ofneural/foraminal stenosis.

In certain preferred embodiments, another stage of the intervertebraldisc implantation method involves initial endplate preparation includingdrilling pilot grooves in the superior and inferior vertebral bodies.After complete distraction has taken place, the distractor shown in FIG.54 is removed. Referring to FIG. 55, the protrusion drill guide of FIGS.20A-20D is inserted into the prepared disc space. The openings at theupper and lower ends of the drill guide are aligned with the proximalends of the reference pins. As shown in FIG. 55, the reference pinsengage the openings for guiding the drill guide toward the prepared discspace. The head at the distal end of the drill guide is inserted intothe prepared disc space until the vertebral body stops abut against theanterior faces of the superior and inferior vertebral bodies. Inpreferred embodiments, the surgeon should visually check that thevertebral body stops of the drill guide come into full contact with thesuperior and inferior vertebral bodies. The handle of the drill guide ispreferably parallel with the inferior and superior endplates and alignedin the sagittal plane.

As shown in FIG. 55, a drill bit is utilized to drill four pilot holesfor the implant protrusions at precise locations in the vertebralbodies. As shown in FIG. 55, the drill guide includes two openings fordrilling a pair of pilot holes in the superior vertebral body and twoopenings for drilling pilot holes in the inferior vertebral body. Incertain preferred embodiments, the drill includes a stop to limit thelength of the pilot holes. In particular preferred embodiments, there isa stop on the drill so as to ensure that the pilot holes are no morethan 10 mm in length.

Referring to FIG. 56, after the pilot holes have been formed in thesuperior and inferior vertebral bodies, the drill guide is retractedfrom the targeted disc space and decoupled from the two reference pins.As shown in FIG. 56, two pilot holes are formed in the superiorvertebral body and two pilot holes are formed in the inferior vertebralbody. The two pilot holes on the left of the adjacent vertebral bodiesare preferably in vertical alignment with one another and the two pilotholes on the right of the vertebral bodies are preferably in verticalalignment with one another.

In certain preferred embodiments, channels for the protrusions of theintervertebral disc implant are formed in the endplates of the superiorand inferior vertebral bodies. Referring to FIG. 57, the chisel guideshown and described in FIGS. 21A-21D is inserted into the targeted discspace. The alignment openings in the chisel guide are slid over thereference pins. The head at the distal end of the chisel guide isinserted into the targeted disc space until the vertebral body stopscome into contact with the anterior surfaces of the vertebral bodies.The handle of the chisel guide is preferably parallel with the superiorand inferior endplates and aligned in the sagittal plane. As shown inFIG. 55, the chisel described in FIGS. 22A-22D is coupled with one ofthe tracks of the chisel guide and advanced toward the disc space. Thecutting blades of the chisel are preferably advanced toward the superiorand inferior vertebral bodies while positive pressure is applied to thechisel guide to ensure that it does not back out of the disc space. FIG.23 shows the chisel 374 coupled with the chisel guide 350 with thecutting blades at the distal end of the chisel opposing the superior andinferior vertebral bodies. A striking instrument, such as the malletshown and described in FIGS. 24A-24B, may be utilized to strike thedistal end of the chisel so as to cut channels in the superior andinferior vertebral bodies.

Referring to FIG. 58, after the first chisel has cut the channels on oneside of the chisel guide, a second chisel is preferably utilized in thesame manner as described above with respect to the first chisel to cut asecond set of channels in the vertebral bodies. FIG. 59 shows thetargeted spinal segment after a set of channels has been cut into thesuperior and inferior vertebral bodies. FIG. 60 shows the targetedspinal segment after the channels have been cut in the vertebral bodiesand the chisel guide has been removed from the reference pins.

In certain preferred embodiments, a sizing operation is conducted todetermine the proper size of the intervertebral disc that will be placedinto the targeted disc space. Referring to FIG. 61, a sizer such as thesizer shown and described above in FIGS. 25A-26B may be inserted intothe disc space. The sizers may have different heights (e.g., 5-9 mm) anddifferent base plate widths (e.g., 14 mm and 16 mm). In preferredembodiments, a sizer having a height of 5 mm is used initially. Thesizer is preferably attached to the handle shown and described above inFIGS. 26A-26D. The sizer is then advanced into the disc space as shownin FIG. 62. The sizer is preferably advanced until the vertebral bodystops on the sizer abut against the anterior surfaces of the superiorand inferior vertebral bodies.

After starting with a sizer having a height of 5 mm, sequentially largersizers are utilized to determine the desired implant height that willbest fit into the disc space without over tensioning the annulus. Thecorrect height for the sizer is preferably determined when the sizerfits snugly into the disc space with mild to moderate resistance toretraction of the sizer. The width of the disc space may also be checkedby using a sizer having a different width and inserting the sizer intothe disc space. In certain preferred embodiments, the sizer may includealignment openings that engage the reference pins for guiding the sizeras it is advanced toward the disc space.

In certain preferred embodiments, a trial is inserted into the discspace to complete preparation of the channels for the protrusions of theintervertebral disc. Referring to FIG. 63, a trial such as that shownand described above in FIGS. 28A-28D is advanced toward the disc space.As described above, the trial includes alignment openings that are slidover the reference pins for guiding advancement of the trial. Theparticular size of the trial is selected based upon the correspondingsize of the sizer that produced the best fit within the disc space. Incertain preferred embodiments, the particular trial selected is basedupon the following chart:

Sizer Trial Size 5-6 mm height Small, 14 mm 14 mm × 12 mm baseplate 7-9mm height Large, 14 mm 14 mm × 12 mm baseplate 5-6 mm height Small, 16mm 16 mm × 14 mm baseplate 7-9 mm height Large, 16 mm 16 mm × 14 mmbaseplate

Referring to FIG. 64, the trial is advanced along the reference pins andinto the intervertebral space. The protrusions on the trial arepreferably aligned with the channels previously formed in the opposingendplates. A mallet may be impacted against the proximal end of thetrial for advancing the trial into the disc space. If necessary, a slaphammer may be utilized to remove the trial from the disc space. Inpreferred embodiments, the trial is inserted at an angle that isparallel to the endplates so as to prevent damage to the endplates andavoid creating bone fragments. One or more trials may be inserted intothe disc space until a proper fit is achieved.

In certain preferred embodiments, an appropriately sized intervertebraldisc implant is then selected and inserted into a targeted disc space.Referring to FIG. 65, in certain preferred embodiments, theintervertebral disc implant is provided as a single unit with the topand bottom elements of the implant being held together by an implantdispenser 456. In preferred embodiments, the implant dispenser is colorcoded to correspond to the height of the implant. In addition, theimplant dispenser is preferably marked with the height of the implantand the width of the top and bottom elements. The outer surface of theimplant may also be marked with the height and width of the implant. Inparticular preferred embodiments, the anterior face of the implant ismarked with the height and width of the implant.

In preferred embodiments, prior to insertion of the intervertebral discimplant, the size label on the implant is inspected and the size labelon the implant dispenser is also inspected to ensure that the correctlysized implant was selected and that the top or superior element of theimplant is oriented for proper insertion. In preferred embodiments, animplant is selected having a height and baseplate dimensions that matchthe corresponding sizer that restored the desired height of the discspace without over-tensioning the annulus or damaging the facets.

After an appropriately sized intervertebral disc implant has beenselected, an inserter head, such as the inserter head shown anddescribed above in FIGS. 30A-30B, is selected. The selected inserterhead preferably has a height and/or dimensions that match the particulardimensions of the selected implant and selected implant dispenser. Thus,the inserter head may also be color coded to correspond to the height ofthe implant and the particular dimensions of the implant dispenser. Theinserter head may be a single use component that is discarded after theimplantation procedure. In certain preferred embodiments, each inserterhead may be used for either a 14 mm or 16 mm width implant that ispreferably matched to the implant height.

Referring to FIGS. 66 and 67, the implant and implant dispenser arejuxtaposed with the distal end of the inserter head.

In certain preferred embodiments, the inserter head is attached to ahandle. The attachment may include a threaded attachment whereby a t-baror handle is rotated to threadably engage the inserter head with thehandle.

Referring to FIG. 67, in certain preferred embodiments, the implant isattached to the inserter head by first matching the superior andinferior labels on the implant dispenser with the inserter head. Thefour arms of the inserter head are then slid along the outer lateralsides of the implant protrusions. The inwardly extending projections onthe arms are preferably engaged with the depressions formed in the outerlateral sides of the protrusions. The implant is preferably secured tothe inserter head when the projections are seated in the depressions inthe outer lateral sides of the protrusions. Once the implant has beensecured to the inserter head, the implant dispenser may be decoupledfrom the implant. Once secured, the posterior part of the implantpreferably extends beyond the ends of the arms of the inserter head. Theimplant dispenser may then be detached from engagement with the implant.

In certain preferred embodiments, the intervertebral disc implant isinserted into a prepared disc space. Referring to FIGS. 68 and 69, theinserter head is properly oriented with the disc space. In preferredembodiments, the inserter head includes at least one label or markingthat is oriented relative to the superior or inferior vertebral bodies.Preferably, a superior label of the inserter head is oriented on top andan inferior label is oriented on the bottom. The reference pins are thenutilized to guide the inserter head toward the disc space. The guidechannels formed at the top and bottom of the inserter head preferablyengage the reference pins. Referring to FIG. 69, as the intervertebraldisc is advanced toward the disc space, the implant protrusions arepreferably aligned with the protrusion channels previously formed in theendplates. In certain preferred embodiments, fluoroscopy is utilized tocheck the angle of insertion of the implant. The inserter head ispreferably advanced toward the disc space until the four arms of theinserter head come into contact with the anterior surfaces of thevertebral bones.

Referring to FIG. 70, a T-handle 496 (FIG. 31) may then be rotated foradvancing a pusher rod 494 which pushes the implant off the distal endof the inserter head. This procedure is shown and described above withrespect to the description of FIGS. 33A-35B. FIG. 35B shows pusher rod494 decoupling intervertebral disc 100 from the distal end of inserterhead 474.

In certain preferred embodiments, the T-handle may be rotatedapproximately three or four turns for advancing the intervertebral discimplant 100 into the disc space. The proximal end of the handle for theinserter head may be impacted to ensure that the intervertebral discimplant continues into the disc space as the four arms of the inserterhead remain in contact with the vertebral bodies. FIG. 71 shows furtheradvancement of the intervertebral disc implant into the disc space. Incertain preferred embodiments, immediately prior to insertion of theintervertebral disc implant, the disc space may be distractedapproximately 2 mm wider than the base plates of the implant tofacilitate insertion. The distraction may result from the grooves on theinserter head being angled relative to one another, as described abovein certain preferred embodiments.

Referring to FIG. 72, insertion is completed when the implant is fullydisengaged from the inserter head and the posterior faces of theanterior walls of the intervertebral disc's top and bottom elements arein contact with the anterior surfaces of the superior and inferiorvertebral bodies. The anterior/posterior positioning of the implant andthe baseplate size are preferably confirmed to be satisfactory usingfluoroscopy. Referring to FIG. 73, if more posterior positioning ofeither the top element or the bottom element of the intervertebral discimplant is required, a tamp such as that shown and described above inFIG. 36A may be utilized for adjusting the position of the implant. Inpreferred embodiments, the tamp may be impacted to adjust theanterior/posterior depth of the top and bottom elements of the implant.The anterior walls of the top and bottom elements serve as vertebralbody stops to prevent the implant from being impacted too farposteriorly. After final insertion and adjustments have been completed,the posterior faces of the anterior walls should be flush with theanterior faces of the respective vertebral bodies.

Referring to FIG. 72, once all relevant tests have been performed toensure that the intervertebral disc is properly positioned within thedisc space, the reference pins may be removed. A biocompatible material,such as a small amount of bone wax, may be applied to the reference pinopenings remaining in the anterior surfaces of the superior and inferiorvertebral bodies.

Referring to FIGS. 75A and 75B, an intraoperative lateral andanterior/posterior image of the implant is preferably obtained toobserve its final position. If the implant is not properly positioned,it may be removed such as by using the extractor shown and describedabove in FIGS. 37A-37D. In FIG. 74, a hook of the extractor is engagedwith an anterior wall of a top element of the intervertebral discimplant. Once it has been confirmed that the intervertebral disc isproperly positioned within the disc space, a standard surgical closureprocedure for anterior spinal surgery may be performed. Prior todischarge from the hospital, a lateral and anterior/posterior X-ray withthe patient in the standing and/or sitting position is preferred.

Following surgery, in certain preferred embodiments, a goal ofpost-operative rehabilitation is to return the patient to normalactivity as soon as possible without jeopardizing soft and hard tissuehealing. Preferably, the patient should wear a soft collar forapproximately 1-2 weeks to support healing of the incision. Thepatient's rehabilitation program may be modified under the direction ofa surgeon to take into consideration the patient's age, stage ofhealing, general health, physical condition, life-style, and activitygoals. Adherence to a recommended rehabilitation program is highlydesirable.

FIGS. 76A-76E show a midline marker 1000 that is used for determining amidline of a disc space between two vertebrae. The midline marker 1000has a cruciform shape with a first vertical extension 1002, a secondvertical extension 1004, a first lateral extension 1006, and a secondlateral extension 1008. The midline marker has a leading face 1010 and atrailing face 1012. As shown in FIG. 76B, the leading face 1010 has aconcave curved surface that extends between the first and second lateralarms 1006, 1008. The first lateral arm 1006 has a first barbed spike1014 projecting therefrom, and the second lateral arm 1008 has a secondbarbed spike 1016 projecting therefrom. The midline marker 1000 includesa button 1018 projecting from the rear surface 1012 there, which isconnected to the midline marker via connector segment 1020. As shown inFIG. 76E, the connector segment 1020 has a rectangular or square crosssection, for reasons that will be described below.

Referring to FIG. 76D, the upper end of the first vertical extension1002 has a concave recess 1022 and the lower end of the second verticalextension 1004 has a concave recess 1024. The concave recesses 1022,1024 provide an alignment feature for marking vertebral bone and/ormaking openings in bone, as will be described in more detail below.

FIGS. 77A-77E show a midline marker handle 1030 for securing the midlinemarker 1000 shown in FIGS. 76A-76E. The midline marker handle 1030includes a proximal end 1032 and a distal end 1034. The midline markerhandle 1030 includes an outer shaft 1036 that extends between theproximal end 1032 and the distal end 1034. Referring to FIGS. 77B and77E, the outer shaft 1036 has at least one slot 1038 formed therein. Theslot 1038 serves as a guide slot, as will be described in more detailbelow. The proximal end 1032 of the outer shaft 1036 has a flange 1040extending therefrom. The flange 1040 is preferably integrally formedwith the outer shaft 1036. Referring to FIG. 77C, the midline markerhandle includes a plunger 1042 that is disposed within the outer shaft1036. The plunger 1042 has a knob 1044 secured to a proximal endthereof. The midline marker handle 1030 also includes a spring 1046disposed between the flange 1040 and the knob 1044 for normally urgingthe plunger into a retracted position.

Referring to FIG. 77E, the distal end of the plunger 1042 includes aU-shaped opening 1048 that is adapted to receive the button 1018projecting from the rear surface 1012 of the midline marker 1000 (FIG.76B).

Referring to FIG. 77C, the plunger 1042 has an aperture 1050 extendingtherethrough and a pin 1052 is disposed within the apertures 1050.Referring to FIG. 77B, the pin 1052 moves with the plunger 1042, and ispositioned within the slot 1038 provided in the outer shaft 1036 forguiding advancement of the plunger relative to the outer shaft 1036.

Referring to FIGS. 77B and 77E, the outer shaft 1036 includes analignment feature 1054 that assists the surgeon in properly aligning themidline marker handle 1030 during a surgical procedure. Referring toFIGS. 77D and 77E, when the midline marker 1000 is secured to themidline marker handle 1030, the concave shaped recesses 1022, 1024 arepreferably aligned with the alignment feature 1052.

Referring to FIG. 77A-77C and 77E, the U-shaped opening 1048 at theproximal end of the plunger 1042 is normally urged into the retractedposition by spring 1046. In order to overcome the force of the spring1046 and advance the U-shaped opening 1048 so that it projects beyondthe distal end of the outer shaft 1036, a surgeon will grasp the flange1040 and urge the knob 1044 toward the distal end 1034 of the midlinemarker handle 1030. When the surgeon overcomes the force of the spring1046, the plunger 1042 will move toward the distal end 1034 of the toolso as to project the U-shaped opening 1048 beyond the distal end of theouter shaft 1036.

FIGS. 78A and 78B show advancement of the U-shaped opening 1048 beyondthe distal end of the outer shaft 1036. In FIG. 78A, the plunger 1042 isin its normal retracted position so that the U-shaped opening 1048 lieswithin the distal end 1034 of the tool 1030. In FIG. 78B, the plunger1042 is urged toward the distal end 1034 of the tool so that theU-shaped opening 1048 is moved beyond the distal end of the tool. Atthat point, the button 1018 (FIG. 76B) of the midline marker may beinserted into the U-shaped opening 1048. The plunger 1042 is thenallowed to retract toward the proximal end of the tool so that theplunger moves back to the position shown in FIG. 78A. At that point, thebutton of the midline marker is captured in the U-shaped opening 1048whereby the midline marker is coupled to the distal end of the midlinemarker handle 1030. FIGS. 77A-77C show the midline marker after it hasbeen secured to the distal end 1034 of the midline marker handle 1030.

After the midline marker 1000 has been secured to the distal end of themidline marker handle 1030, the spikes 1014, 1016 (FIG. 76B) arepreferably inserted into an intervertebral disc between opposingvertebrae.

FIGS. 79A-79D show a reference pin drill and insertion guide, inaccordance with certain preferred embodiments of the present invention.The reference pin drill and insertion guide 1060 has a proximal end1062, a distal end 1064, a handle 1066 at the proximal end 1062, a shaft1068 that projects from a leading end of the handle 1066, and a head1070 secured to a leading end the shaft 1068.

Referring to FIGS. 79A and 79B, the shaft 1068 preferably has an elbow1072 forming an angle of approximately one hundred fifty (150) degrees.The elbow provides an angled shaft that enables the handle 1066 to belocated out of alignment with the head 1070 for enhancing visibility ofthe head 1070 duping a surgical procedure.

Referring to FIG. 79D, the head 1070 of the reference pin drill andinsertion guide 1060 includes a tapered nose 1074 that is insertableinto a disc space. The tapered nose 1074 includes a top surface 1076adapted to engage an upper vertebral body and a bottom surface 1078adapted to engage a lower vertebral body. The tapered nose 1074 isinserted into the disc space with the top surface 1076 engaging a firstvertebral body and the bottom surface 1078 engaging a second vertebralbody. The head 1070 includes a first vertebral body stop 1080 extendingalong one side of the head and a second vertebral body stop 1082extending along an opposite side of the head 1070. The vertebral bodystops are adapted to engage vertebral bone for preventing over-insertionof the guide 1060 into a disc spaces.

Referring to FIG. 79C, the first vertebral body stop 1080 has an upperend 1084 that extends above the top surface 1076 of the tapered nose1074 and a lower end 1086 that extends below the bottom surface 1078 ofthe tapered nose 1074. Similarly, the second vertebral body stop 1082has an upper end 1088 that extends above the top surface 1076 of thetapered nose 1074 and a lower end 1090 that extends below the bottomsurface 1078 of the tapered nose 1074. The upper ends 1084, 1088 of therespective vertebral body contacts 1080, 1082 extend approximately two(2) millimeters above the top surface 1076 of the tapered nose 1074. Thelower ends 1086, 1090 of the respective vertebral body stops 1080, 1082extend approximately two (2) millimeters below the bottom surface 1078of the tapered nose 1074. In the preferred embodiment, the vertebralbody stops preferably have a height of approximately two (2)millimeters. The enhanced size of the vertebral body stops improves thestability of the reference pin drill and insertion guide when drillingholes in the vertebral bone and inserting reference pins.

Referring to FIG. 79B, the leading faces 1092, 1094 of the vertebralbody stops 1080 1082 have concave curved surfaces that generally conformto the outer surfaces of the vertebrae. The concave curved surfaces alsoenhance stability of the guide 1060 as described above.

Referring to FIGS. 79A and 79D, the head 1070 includes a firstprotective sheath 1096 including a central opening 1098 and a slot 1100.The first protective sheath 1096 is disposed over the top surface 1076of the tapered nose 1074. The head 1070 also includes a secondprotective sheath 1102 having a central 1104 extending therethrough anda slot 1106.

Referring to FIG. 79D, the first and second protective sheaths 1096,1102 enable reference pin holes to be safely and effectively drilled invertebral bone. The sheaths 1096, 1102 protect the surrounding tissue asdrill bits reference pins and/or driving instruments are insertedthrough the sheaths. The openings 1098, 1104 extending through therespective sheaths 1096, 1102 are adapted to receive drill bits,sleeves, and reference pin drivers that enable reference pins to beinserted into openings formed in the vertebrae. Although the presentinvention is not limited by any particular theory of operation, it isbelieved that the slots 1100, 1106 provided on the sheaths enable asurgeon to visibly observe advancement of drill bits, reference pindrivers, sleeves, and/or any tools used to formed the openings in thevertebral bone or insert the reference pins in the openings.

FIGS. 80A and 80B show a step drill for use with the reference pin drilland insertion guide 1060 shown in FIGS. 79A-79B. The step drill 1120includes a shaft 1122 having a proximal end 1124 and a distal end 1126.The proximal end 1124 is adapted to be coupled with an instrument thatrotates the shaft 1122. The proximal end of the step drill includes adrill bit 1128 and a step structure 1130 that extends between the drillbit 1128 and a stop flange 1132. The step drill 1120 includes acylindrical surface 1134 having an outer diameter that substantiallymatches the inner diameter of the openings 1098, 1104 of the protectivesheaths 1096, 1102 (FIG. 79D).

Referring to FIG. 81, after the distal end 1126 of the step drill 1122is inserted into the opening 1098 of the protective sheath 1096, thestep drill may be advanced until the stop flange 1132 abuts against thesheath 1096. As the step drill is rotated, the drill bit 1128 forms anopening in the vertebral body for receiving a reference pin.

FIG. 82 shows a driver 1140 having a shaft 1142 extending from a forwardend of a handle. The shaft 1142 has an opening at a distal end 1144thereof. The opening at the distal end 1144 receives a reference pin1145 having threads 1146. The shaft 1142 of the driver 1140 isinsertable into the opening of the protective sheath 1096 for anchoringthe reference pin 1145 in vertebral bone. The handle of the driver 1140is rotated for threading the reference pin 1145 into the opening in thevertebral body.

FIG. 83 shows a step drill 1220 in accordance with another preferredembodiment of the present invention. The step drill 1220 includes ashaft 1222 having a proximal end 1224 and a distal end 1226. The stepdrill includes a drill bit 1228 at the distal end 1226, a first section1230 having a first diameter that is larger than the diameter of thedrill bit section 1228, and a second section 1232 having a seconddiameter that is larger than the first diameter of the first section1230.

Referring to FIGS. 84A and 84B, a reference pin drill guide 1260 usedfor forming openings in vertebral bone has a proximal end 1262 and adistal end 1264. The reference pin drill guide includes a handle 1266, ashaft 1268 and a head 1270. The shaft includes an elbow 1272 thatprovides an angle in the shaft of approximately one hundred fifty (150)degrees. The head 1270 includes a tapered nose 1274 insertible into adisc space. The plug includes a top surface 1276 and a bottom surface1278, which are adapted to be inserted between opposing faces ofvertebrae.

The head 1270 includes a first vertebral body stop 1280 projecting fromone side of the head 1270 and a second vertebral body stop 1282projecting from an opposite side of the head. The first vertebral bodystop 1280 includes an upper end 1284 that projects above the top surface1276 of the tapered nose 1274 and a lower end 1286 that projects belowthe bottom surface 1278 of the tapered nose 1274. The second vertebralbody stop 1282 includes an upper end 1288 that projects above the topsurface 1276 of the tapered nose 1274 and a lower end 1290 that projectsbelow the bottom surface 1278 of the tapered nose 1274. Referring toFIG. 84A, the leading faces 1292, 1294 of the respective first andsecond vertebral body stops 1280, 1282 have a concave curve forconforming to the outer surfaces of the vertebral bone. The upper ends1284, 1288 of the respective vertebral body contacts 1280, 1282 extendapproximately two (2) millimeters above the top surface 1276 of thetapered nose 1274. The lower ends 1286, 1290 of the respective vertebralbody stops 1280, 1282 extend approximately two (2) millimeters below thebottom surface 1278 of the tapered nose 1274. In the preferredembodiment, the vertebral body stops preferably have a height ofapproximately two (2) millimeters.

Referring to FIGS. 85A and 85B, the head 1270 of the reference pin drillguide 1260 includes a first protective sheath 1296 having an openingextending therethrough and a slot 1300 formed in the side of the firstprotective sheath. The head 1270 includes a second protective sheath1302 having an opening extending therethrough and a slot 1306 formed inthe side of the second protective sheath. The openings in the respectivefirst and second protective sheaths 1296, 1302 are designed to receivethe step drill 1220 shown in FIG. 83.

FIGS. 85A and 85B show the step drill 1220 inserted into the openingextending through the first protective sheath 1296. The step drill 1220may be advanced until the shoulder between the first step section 1230and the second step section 1232 (FIG. 83) engages the trailing end ofthe first protective sheath 1296. The step drill 1220 may be rotated sothat the drill bit 1228 forms an opening in vertebral bone.

FIGS. 86A and 86B show the formation of openings in vertebral bone forreference pins, in accordance with certain preferred embodiments of thepresent invention. Referring FIG. 86A, the tapered nose 1274 of thereference pin drill guide 1260 shown in FIG. 85A is inserted into a discspace between opposing vertebrae. The tapered nose 1274 is advanceableinto the disc space until the vertebral body stop 1282 abuts againstvertebral bone. Once the vertebral body stop abuts against the vertebralbone, the head 1270 cannot be further advanced into the disc space. Thestep drill 1220 is then inserted into the opening of the firstprotective sheath 1296, and advanced into vertebral bone to formreference pin openings in the vertebral bone. The slot 1300 in theprotective sheath 1296 enables the surgeon to visibly monitor theadvancement of the drill bit 1228 into the vertebral bone. The slot 1300may also be used to monitor the advancement of a reference pin into thebone.

FIGS. 87A-87D show a fin drill guide 1314 that is generally similar tothe drill guide shown above in FIGS. 20A-20D described above. The findrill guide 1314 shown in FIGS. 87A-87D includes vertebral body stops1380, 1382 that extend laterally from opposite sides of head 1370.Referring to FIGS. 87C and 87D, the first vertebral body stop 1380includes an upper end 1384 that extends above a top surface 1376 oftapered nose 1374 and a lower end 1386 that extends below the bottomsurface 1378 of tapered nose 1374. The second vertebral body stop 1382includes an upper end 1388 that extends above the top surface 1376 and alower end 1390 that extends below the bottom surface 1378. In thepreferred embodiment, the vertebral body stops have a height ofapproximately two (2) millimeters. Referring to FIG. 87B, the leadingfaces 1392, 1394 of the respective first and second vertebral body stops1380, 1382 have concave surfaces that generally conform to the outersurfaces of vertebral bodies. The upper ends 1384, 1388 of therespective vertebral body contacts 1380, 1382 extend approximately two(2) millimeters above the top surface 1376 of the tapered nose 1374. Thelower ends 1386, 1390 of the respective vertebral body stops 1380, 1382extend approximately two (2) millimeters below the bottom surface 1378of the tapered nose 1374.

During a surgical procedure for preparing a disc space for receiving animplant, the tapered nose 1374 is inserted into a disc space until thefirst and second vertebral body stops 1380, 1382 abut against the outersurfaces of vertebral bodies. The engagement of the first and secondvertebral body stops 1380, 1382 with the vertebral bone prevents furtheradvancement of the tool. A drill 1322 may then be advanced through theopenings in the head 1370 for preparing the disc space, as describedabove.

FIGS. 88A-88D show a chisel guide 1450 that is similar to the chiselguide shown and described above in FIGS. 21A-21D. The chisel guide 1450includes a head 1466 that is insertible into a disc space, a firstvertebral body stop 1480 provided on a first lateral side of the head1466 and a second vertebral body stop 1482 provided on a second lateralside of the head 1466. The first vertebral body stop 1480 has an upperend 1484 that extends above a top surface of the head 1466 and a lowerend 1486 that extends below a bottom surface of the head 1466. Thesecond vertebral body stop 1482 includes an upper end 1488 that extendsabove the top surface of the head 1466 and a lower end 1490 that extendsbelow the bottom surface of the plug 1466. The respective upper ends1484, 1488 of the vertebral body stops 1480, 1482 extend approximatelytwo (2) millimeters over the top surface of the head 1466, and therespective lower ends 1486, 1490 of the first and second vertebral bodystops 1480, 1482 extend approximately two (2) millimeters below thebottom surface of the head 1466. The vertebral body stops preferablyabut against the outer surfaces of the opposing vertebrae for providinglateral stability for the chisel guide. As a result, the chisel guidewill generally remain stable, in place and will not move relative to thevertebral bodies during a bone chiseling step.

Referring to FIG. 88A, the chisel guide 1450 also includes a handle 1494provided at a proximal end thereof and a depression 1496 formed in thehandle 1494. As will be described in more detail below, the depression1496 provides additional room for advancement of a chisel toward thedistal end of the chisel guide 1450.

FIG. 89 shows the head 1466 at the distal end of the chisel guide 1450after being inserted into a disc space. Reference pin 1464 (anchored ina vertebral body) guides advancement of the chisel guide toward the discspace. The distal end of the chisel guide is advanced into the discspace until the first and second vertebral body stops 1480, 1482 abutagainst the outer surfaces of the vertebral bodies. A chisel 1474,similar to that described above in FIGS. 22A-22D, is coupled with thechisel guide. The chisel 1474 is advanced into bone by striking the knob1475 at the distal end thereof. The depression 1496 provided at theproximal end of the handle 1494 enables further advancement of thechisel 1474 toward the disc space. The depth of the cut ultimately madeis limited by the chisel impaction head contacting the handle of thechisel guide.

FIGS. 90A-90D show a sizer 1508 that is generally similar to the sizershown above in FIGS. 25A-25D. The sizer 1508 includes a main body 1510having a distal end 1512, a top surface 1514, and a bottom surface 1516.The main body includes beveled surfaces 1518, 1519 extending between thedistal end 1512 and the top and bottom surfaces 1514, 1516 to easeinsertion of the sizer between opposing vertebrae. The sizer 1508includes an adapter shaft 1520 and first and second projections 1522A,1522B provided on the adapter shaft 1520.

The sizer 1508 also includes vertebral body stop 1524 and 1526 forlimiting insertion of the sizer into a disc space. The first vertebralbody stop 1524 includes a depression or cutout 1525 that providesclearance for reference pins 264 or other tools. The second vertebralbody stop 1526 also includes a depression or cutout 1527 for providingclearance for a reference pin 264. The upper and lower beveled surfaces1518, 1519 extend approximately one (1) millimeter from the distal end1512. The beveled surfaces 1518, 1519 form an angle of approximatelytwenty seven (27) degrees.

FIGS. 91A-91C show a handle 1532 that is generally similar to that shownand described above in FIGS. 26C-26D. The sizer of FIGS. 90A-90D issecured to the distal end of the handle 1532. FIGS. 92A and 92B show thedistal end of the handle 1532 with the sizer 1508 coupled to the handle.The sizer 1508 may be attached to the handle 1532 by sliding theprojections 1522A, 1522B into the grooves extending from the distal end1530 of the handle 1532. Referring to FIG. 91C, after the sizer 1508 iscoupled with the handle 1532, a rotatable element 1534 may be rotatedfor locking the sizer 1508 to the handle 1532.

Referring to FIGS. 93A-93D, in certain preferred embodiments of thepresent invention, a trial or serrated broach 1636 includes a proximalend 1638, a distal end 1640, a shaft 1642 extending between the distaland proximal ends, and a striking surface 1644 located at the proximalend 1638 thereof. The serrated broach also includes a head 1646 securedto the distal end 1638. The head 1646 includes protrusions 1648 havingteeth 1650 that are positioned to coincide with the protrusions of anintervertebral implant in order to ensure proper orientation. The sizeof the serrated broach 1636 that is selected for use is based upon thelargest sizer that safely fit within the intervertebral disc space. Theserrated broach 1636 also includes reference pin alignment openings 1652and 1654, which are adapted to slide over reference pins secured tovertebral bone.

The serrated broach 1636 includes a first vertebral body stop 1680 and asecond vertebral body stop 1682 projecting from opposite sides of thehead 1646. The first vertebral body stop 1680 includes an upper end 1688that projects above a top surface of the head 1646 and a lower end 1690that projects below a bottom surface of the head 1646. The secondvertebral body stop 1682 includes an upper end 1688 that projects abovea top surface of the head 1646 and a lower end 1690 that projects belowa bottom surface of the head 1646. The upper ends of the vertebral bodystops 1680, 1682 project approximately two (2) millimeters over the topsurface of the head 1646. The lower ends 1686, 1690 extendsapproximately two (2) millimeters below the bottom surface of the head1646. The vertebral body stops 1680, 1682 preferably have a height ofabout two (2) millimeters.

Referring to FIGS. 94A-94F, in accordance with certain preferredembodiments of the present invention, an implant dispenser 1756 isadapted to hold the top and bottom elements of an intervertebral discimplant 100 as a single unit with the articulating surfaces heldtogether. Referring to FIGS. 94A-94C, the implant dispenser 1756 ispreferably flexible and includes a superior arm 1758 for engaging a topelement of an intervertebral disc implant and an inferior arm 1764 forengaging a bottom element of an intervertebral disc implant. Thesuperior and inferior arms preferably have lateral notches 1762 formedtherein for receiving the teeth of the top and bottom elements. Theimplant dispenser preferably includes a central support 1764 thatenables the superior and inferior arms 1758, 1760 to flex relative toone another and to move away from one another for releasing anintervertebral disc implant.

Referring to FIGS. 94A, 94B, 94D and 94E, the superior arm 1758 includesa slot 1775 formed therein. Referring to FIG. 94C, the inner surface ofthe superior arm 1758 has a first notch 1777 formed therein and theinterior surface of the inferior arm 1760 has a second notch 1779 formedtherein.

FIGS. 95A-95C show a clip 1781 that is insertible between the superiorand inferior arms of the implant dispenser shown in FIGS. 94A-94F. Theclip 1781 includes a main body 1783 having an upper end 1785 and a lowerend 1787. The upper and lower ends 1785, 1787 of the main body 1783preferably conform to the notches 1777, 1779 formed in the innersurfaces of the superior and inferior arms 1758, 1760 of the implantdispenser 1756. The clip 1781 includes a projection 1789 that extendsupwardly from the main body 1783. The projection 1789 is adapted to fitwithin the slot 1775 formed in the superior arm 1758 of the implantdispenser 1756 so as to prevent the superior and inferior arms frombeing moved toward one another.

FIGS. 96A-96E show the clip 1781 disposed between the superior arm 1758and the inferior arm 1760 of the implant dispenser 1756, whereby themain body 1783 of the clip 1781 is positioned between the superior andinferior arms 1758, 1760. The upper end 1785 of the main body 1783preferably engages the notch formed in the inner surface of the superiorarm 1758, and the lower end 1787 of the main body 1783 is preferablyengaged with the notch formed in the inner surface of the inferior arm1760. Referring to FIGS. 96A-96C, the projection 1789 preferably extendsthrough the slot 1775 formed in the superior arm 1758. When in placebetween the arms 1758, 1760, the clip 1781 prevents the superior andinferior arms 1758, 1760 from moving toward one another. The clip 1781is preferably in place between the arms during transport and storage ofthe implant/implant dispenser assembly. As a result, when the clip is inplace, the superior and inferior arm 1758, 1760 cannot be moved towardsone another so as to accidentally dispense or dislodge the implant.

FIGS. 97A-97F and 98A-98B show an implant insertion tool 1800 forinserting an intervertebral disc implant, such as the implant shownabove in FIGS. 1-6B. Referring to FIGS. 97A-97C, the implant insertiontool 1800 includes an inserter body 1802 having a proximal end 1804 anda distal end 1806. The implant insertion tool 1800, which is preferablymade of a biocompatible material such as titanium, includes an inserterhead 1876 that is integrally connected with the inserter body 1802. Thedistal end 1878 of the inserter head 1876 includes four spaced arms 1882having inwardly facing surfaces with projections 1884 that are adaptedto fit within the depressions formed within the protrusions of the topand bottom elements of the intervertebral disc implant. Referring toFIG. 97D, the inserter head 1876 includes a central opening 1886extending therethrough. Referring to FIGS. 97A and 97D, the inserterhead 1876 includes an upper alignment groove 1888 and a lower alignmentgroove 1890. The alignment grooves 1888, 1890 are adapted to engage thereference pins for guiding advancement of the inserter head. In certainpreferred embodiments, the alignment grooves 1888, 1890 taper toward oneanother so that the grooves are closer to one another at distal endsthereof and farther away from one another at proximal ends thereof. Thetaper of the grooves 1888, 1890 will cause the anchored reference pinsto move away from one another as the insertion tool is moved toward thedisc space thereby providing distraction in order to aid in implantinsertion.

FIG. 97E shows the projection 1884 on one of the four arms 1882. Asnoted above, the projections 1884 on the arms 1882 engage thedepressions (e.g. reference number 121 in FIG. 2C) in the protrusions ofthe top and bottom elements of the intervertebral discs.

FIGS. 98A and 98B show vertebral body stops 1892 provided at the distalends of the arms 1882. The vertebral body stops 1892 are designed toabut against vertebral bone to prevent over-insertion of anintervertebral implant into a disc space.

FIGS. 99A and 99B show the implant dispenser 1756 of FIG. 96C holding anintervertebral disc implant 1000, and transferring the implant 1900 tothe arms 1882 of the implant insertion tool 1800. Referring to FIG. 99B,the depressions formed in the protrusions of the implant are coupledwith the projections on the arms 1882 of the inserter head 1874. Theinsertion tool 1800 is coupled to an insertion tool handle 1893 having aplunger rod 1894 extending therethrough. The distal end of the plungerrod 1894 includes a knob 1895 having a contact surface 1896 that may beengaged for advancing the plunger rod 1894 toward the distal end of thetool. Referring to FIGS. 100A and 100B, after the implant 1900 has beensecured to the arms 1882 of the inserter head 1876, the implantdispenser may be removed. Referring to FIG. 100B, at this point, theimplant 1000 is held by the arms 1882 of the inserter head. Referring toFIGS. 101A-101B, the pusher rod 1894 may be advanced toward the distalend of the inserter head 1874 for decoupling the implant 1000 from thearms 1882 of the inserter head 1874. Central slot 1806′ (shown in FIG.97B) preferably allows the arms to flex laterally, thereby allowinginsertion and release of the implant.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

The invention claimed is:
 1. An insertion tool for inserting anintervertebral disc implant between first and second vertebral bodiescomprising: an inserter body having a first slot; and an inserter headintegrally connected with the inserter body, the inserter headincluding: a second slot; a first arm including a first inwardly facingsurface having a first projection extending transversely therefrom and afirst vertebral body stop adapted to abut against the first vertebralbody to prevent over-insertion of the intervertebral disc implant duringinsertion, the first projection adapted to engage a first depression ofthe intervertebral disc implant; a second arm including a secondinwardly facing surface having a second projection extendingtransversely therefrom and a second vertebral body stop adapted to abutagainst the first vertebral body to prevent over-insertion of theintervertebral disc implant during insertion, the second projectionadapted to engage a second depression of the intervertebral discimplant; a raised upper alignment groove extending along a longitudinalaxis of the insertion tool; and a raised lower alignment grooveextending along the longitudinal axis, wherein the first and secondslots form a first continuous slot and the upper and lower alignmentgrooves are tapered with respect to each other.
 2. The insertion tool ofclaim 1, further comprising a third arm and a fourth arm.
 3. Theinsertion tool of claim 2, wherein the third arm includes a thirdprojection adapted to engage a third depression of the intervertebraldisc implant, and the fourth arm includes a fourth projection adapted toengage a fourth depression of the intervertebral disc implant.
 4. Theinsertion tool of claim 3, wherein the inserter body includes a thirdslot and the inserter head includes a fourth slot, the third and fourthslots forming a second continuous slot.
 5. The insertion tool of claim4, wherein the first and second arms are capable of moving with respectto each other and the third and fourth arms are capable of moving withrespect to each other.
 6. The insertion tool of claim 5, wherein thefirst continuous slot is in communication with a first aperture and thesecond continuous slot is in communication with a second aperture. 7.The insertion tool of claim 1, further comprising an insertion toolhandle.
 8. The insertion tool of claim 7, wherein the insertion toolhandle includes a plunger rod extending therethrough.
 9. The insertiontool of claim 8, wherein the plunger rod includes a knob having acontact surface for moving the plunger rod within the insertion toolhandle.
 10. The insertion tool of claim 1, wherein the upper and loweralignment grooves each include a floor surface, the floor surfacesextending along a length of the longitudinal axis of the insertion tooland being angled with respect to one another.
 11. The insertion tool ofclaim 10, wherein the floor surfaces are adapted to contact respectiverods so that the rods are distracted as the insertion tool is movedtowards the first and second vertebral bodies.